Kathryn Moler

All Publications

• Vortex dynamics induced by scanning SQUID susceptometry PHYSICAL REVIEW B Bishop-Van Horn, L., Mueller, E., Moler, K. A. 2023; 107 (22)

  View details for DOI 10.1103/PhysRevB.107.224509

  View details for Web of Science ID 001055185500006

• Superconducting vortices carrying a temperature-dependent fraction of the flux quantum. Science (New York, N.Y.) Iguchi, Y., Shi, R. A., Kihou, K., Lee, C., Barkman, M., Benfenati, A. L., Grinenko, V., Babaev, E., Moler, K. A. 2023: eabp9979

  Abstract

  Magnetic field penetrates type-II bulk superconductors by forming quantum vortices that enclose a magnetic flux equal to the magnetic flux quantum. The flux quantum is a universal quantity that depends only on fundamental constants. Here we investigate isolated vortices in the hole-overdoped Ba1-xKxFe2As2 (x = 0.77) by using scanning superconducting quantum interference device (SQUID) magnetometry. In many locations, we observed vortices that carried only part of a flux quantum, with a magnitude that varied continuously with temperature. We interpret these features as quantum vortices with non-universally quantized (fractional) magnetic flux whose magnitude is determined by the temperature-dependent parameters of a multiband superconductor. The demonstrated mobility and manipulability of the fractional vortices may enable applications in fluxonics-based computing.

  View details for DOI 10.1126/science.abp9979

  View details for PubMedID 37262195

• Microscopic Imaging Homogeneous and Single Phase Superfluid Density in UTe_{2}. Physical review letters Iguchi, Y., Man, H., Thomas, S. M., Ronning, F., Rosa, P. F., Moler, K. A. 2023; 130 (19): 196003

  Abstract

  Odd-parity superconductor UTe_{2} shows spontaneous time-reversal symmetry breaking and multiple superconducting phases, which imply chiral superconductivity, but only in a subset of samples. Here we microscopically observe a homogeneous superfluid density n_{s} on the surface of UTe_{2} and an enhanced superconducting transition temperature near the edges. We also detect vortex-antivortex pairs even at zero magnetic field, indicating the existence of a hidden internal field. The temperature dependence of n_{s}, determined independent of sample geometry, does not support point nodes along the b axis for a quasi-2D Fermi surface and provides no evidence for multiple phase transitions in UTe_{2}.

  View details for DOI 10.1103/PhysRevLett.130.196003

  View details for PubMedID 37243629

• SuperScreen: An open-source package for simulating the magnetic response of two-dimensional superconducting devices COMPUTER PHYSICS COMMUNICATIONS Bishop-Van Horn, L., Moler, K. A. 2022; 280

  View details for DOI 10.1016/j.cpc.2022.108464

  View details for Web of Science ID 000863271300005

• Local imaging of diamagnetism in proximity-coupled niobium nanoisland arrays on gold thin films PHYSICAL REVIEW B Horn, L., Zhang, I. P., Waite, E. N., Mondragon-Shem, I., Jensen, S., Oh, J., Lippman, T., Durkin, M., Hughes, T. L., Mason, N., Moler, K. A., Sochnikov, I. 2022; 106 (5)

  View details for DOI 10.1103/PhysRevB.106.054521

  View details for Web of Science ID 000875057900004

• Local observation of linear-T superfluid density and anomalous vortex dynamics in URu2Si2 PHYSICAL REVIEW B Iguchi, Y., Zhang, I. P., Bauer, E. D., Ronning, F., Kirtley, J. R., Moler, K. A. 2021; 103 (22)

  View details for DOI 10.1103/PhysRevB.103.L220503

  View details for Web of Science ID 000661498500003

• Moving academic research forward during COVID-19 SCIENCE Wigginton, N. S., Cunningham, R. M., Katz, R. H., Lidstrom, M. E., Moler, K. A., Wirtz, D., Zuber, M. T. 2020; 368 (6496): 1190-1192

  View details for DOI 10.1126/science.abc5599

  View details for Web of Science ID 000544031400019

  View details for PubMedID 32467332

• Influence of Resonances on the Noise Performance of SQUID Susceptometers. Sensors (Basel, Switzerland) Davis, S. I., Kirtley, J. R., Moler, K. A. 2019; 20 (1)

  Abstract

  Scanning Superconducting Quantum Interference Device (SQUID) Susceptometry simultaneously images the local magnetic fields and susceptibilities above a sample with sub-micron spatial resolution. Further development of this technique requires a thorough understanding of the current, voltage, and flux ( I V Phi ) characteristics of scanning SQUID susceptometers. These sensors often have striking anomalies in their current-voltage characteristics, which we believe to be due to electromagnetic resonances. The effect of these resonances on the performance of these SQUIDs is unknown. To explore the origin and impact of the resonances, we develop a model that qualitatively reproduces the experimentally-determined I V Phi characteristics of our scanning SQUID susceptometers. We use this model to calculate the noise characteristics of SQUIDs of different designs. We find that the calculated ultimate flux noise is better in susceptometers with damping resistors that diminish the resonances than in susceptometers without damping resistors. Such calculations will enable the optimization of the signal-to-noise characteristics of scanning SQUID susceptometers.

  View details for DOI 10.3390/s20010204

  View details for PubMedID 31905901

• Semiconductor-Ferromagnetic Insulator-Superconductor Nanowires: Stray Field and Exchange Field. Nano letters Liu, Y., Vaitiekenas, S., Marti-Sanchez, S., Koch, C., Hart, S., Cui, Z., Kanne, T., Khan, S. A., Tanta, R., Upadhyay, S., Cachaza, M. E., Marcus, C. M., Arbiol, J., Moler, K. A., Krogstrup, P. 2019

  Abstract

  Nanowires can serve as flexible substrates for hybrid epitaxial growth on selected facets, allowing for the design of heterostructures with complex material combinations and geometries. In this work we report on hybrid epitaxy of freestanding vapor-liquid-solid grown and in-plane selective area grown semiconductor-ferromagnetic insulator-superconductor (InAs/EuS/Al) nanowire heterostructures. We study the crystal growth and complex epitaxial matching of wurtzite and zinc-blende InAs/rock-salt EuS interfaces as well as rock-salt EuS/face-centered cubic Al interfaces. Because of the magnetic anisotropy originating from the nanowire shape, the magnetic structure of the EuS phase is easily tuned into single magnetic domains. This effect efficiently ejects the stray field lines along the nanowires. With tunnel spectroscopy measurements of the density of states, we show that the material has a hard induced superconducting gap, and magnetic hysteretic evolution which indicates that the magnetic exchange fields are not negligible. These hybrid nanowires fulfill key material requirements for serving as a platform for spin-based quantum applications, such as scalable topological quantum computing.

  View details for DOI 10.1021/acs.nanolett.9b04187

  View details for PubMedID 31769993

• Exploring possible ferromagnetism of the LaAlO3/SrTiO3 interface PHYSICAL REVIEW MATERIALS Wittlich, P., Boschker, H., Asaba, T., Li, L., Noad, H. L., Watson, C. A., Moler, K. A., Daraselia, D., Japaridze, D., Shengelaya, A., Wang, J., Xia, J., Mannhart, J. 2019; 3 (10)

  View details for DOI 10.1103/PhysRevMaterials.3.104418

  View details for Web of Science ID 000491485900002

• Current-phase relations of InAs nanowire Josephson junctions: From interacting to multimode regimes PHYSICAL REVIEW B Hart, S., Cui, Z., Menard, G., Deng, M., Antipov, A. E., Lutchyn, R. M., Krogstrup, P., Marcus, C. M., Moler, K. A. 2019; 100 (6)

  View details for DOI 10.1103/PhysRevB.100.064523

  View details for Web of Science ID 000482580900010

• Imaging anisotropic vortex dynamics in FeSe PHYSICAL REVIEW B Zhang, I. P., Palmstrom, J. C., Noad, H., Bishop-Van Horn, L., Iguchi, Y., Cui, Z., Mueller, E., Kirtley, J. R., Fisher, I. R., Moler, K. A. 2019; 100 (2)

  View details for DOI 10.1103/PhysRevB.100.024514

  View details for Web of Science ID 000476686700006

• Modulation of Superconducting Transition Temperature in LaAlO3/SrTiO3 by SrTiO3 Structural Domains JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM Noad, H., Wittlich, P., Mannhart, J., Moler, K. A. 2019; 32 (4): 821–25

  View details for DOI 10.1007/s10948-018-4730-8

  View details for Web of Science ID 000469476200005

• Cryogen-free variable temperature scanning SQUID microscope. The Review of scientific instruments Bishop-Van Horn, L. n., Cui, Z. n., Kirtley, J. R., Moler, K. A. 2019; 90 (6): 063705

  Abstract

  Scanning Superconducting QUantum Interference Device (SQUID) microscopy is a powerful tool for imaging local magnetic properties of materials and devices, but it requires a low-vibration cryogenic environment, traditionally achieved by thermal contact with a bath of liquid helium or the mixing chamber of a "wet" dilution refrigerator. We mount a SQUID microscope on the 3 K plate of a Bluefors cryocooler and characterize its vibration spectrum by measuring SQUID noise in a region of sharp flux gradient. By implementing passive vibration isolation, we reduce relative sensor-sample vibrations to 20 nm in-plane and 15 nm out-of-plane. A variable-temperature sample stage that is thermally isolated from the SQUID sensor enables the measurement at sample temperatures from 2.8 K to 110 K. We demonstrate these advances by imaging inhomogeneous diamagnetic susceptibility and vortex pinning in optimally doped yttrium barium copper oxide above 90 K.

  View details for DOI 10.1063/1.5085008

  View details for PubMedID 31255038

• Micron-scale measurements of low anisotropic strain response of local T-c in Sr2RuO4 PHYSICAL REVIEW B Watson, C. A., Gibbs, A. S., Mackenzie, A. P., Hicks, C. W., Moler, K. A. 2018; 98 (9)

  View details for DOI 10.1103/PhysRevB.98.094521

  View details for Web of Science ID 000445724200007

• Observation of signatures of subresolution defects in two-dimensional superconductors with a scanning SQUID PHYSICAL REVIEW B Noad, H., Watson, C. A., Inoue, H., Kim, M., Sato, H. K., Bell, C., Hwang, H. Y., Kirtley, J. R., Moler, K. A. 2018; 98 (6)

  View details for DOI 10.1103/PhysRevB.98.064510

  View details for Web of Science ID 000450499400004

• Spatially modulated susceptibility in thin film La2-xBaxCuO4 PHYSICAL REVIEW B Davis, S. I., Ullah, R. R., Adamo, C., Watson, C. A., Kirtley, J. R., Beasley, M. R., Kivelson, S. A., Moler, K. A. 2018; 98 (1)

  View details for DOI 10.1103/PhysRevB.98.014506

  View details for Web of Science ID 000438186100003

• A micro-SQUID with dispersive readout for magnetic scanning microscopy APPLIED PHYSICS LETTERS Foroughi, F., Mol, J., Mueller, T., Kirtley, J. R., Moler, K. A., Bluhm, H. 2018; 112 (25)

  View details for DOI 10.1063/1.5030489

  View details for Web of Science ID 000435987400035

• Spatially modulated magnetic structure of EuS due to the tetragonal domain structure of SrTiO3 PHYSICAL REVIEW MATERIALS Rosenberg, A. J., Katmis, F., Kirtley, J. R., Gedik, N., Moodera, J. S., Moler, K. A. 2017; 1 (7)

  View details for DOI 10.1103/PhysRevMaterials.1.074406

  View details for Web of Science ID 000418773400002

• Current-phase relations of few-mode InAs nanowire Josephson junctions NATURE PHYSICS Spanton, E. M., Deng, M., Vaitiekenas, S., Krogstrup, P., Nygard, J., Marcus, C. M., Moler, K. A. 2017; 13 (12): 1177-+

  View details for DOI 10.1038/NPHYS4224

  View details for Web of Science ID 000417049400015

• Imaging quantum materials NATURE MATERIALS Moler, K. 2017; 16 (11): 1049–52

  View details for PubMedID 29066830

• Scanning SQUID sampler with 40-ps time resolution REVIEW OF SCIENTIFIC INSTRUMENTS Cui, Z., Kirtley, J. R., Wang, Y., Kratz, P. A., Rosenberg, A. J., Watson, C. A., Gibson, G. W., Ketchen, M. B., Moler, K. A. 2017; 88 (8): 083703

  Abstract

  Scanning Superconducting QUantum Interference Device (SQUID) microscopy provides valuable information about magnetic properties of materials and devices. The magnetic flux response of the SQUID is often linearized with a flux-locked feedback loop, which limits the response time to microseconds or longer. In this work, we present the design, fabrication, and characterization of a novel scanning SQUID sampler with a 40-ps time resolution and linearized response to periodically triggered signals. Other design features include a micron-scale pickup loop for the detection of local magnetic flux, a field coil to apply a local magnetic field to the sample, and a modulation coil to operate the SQUID sampler in a flux-locked loop to linearize the flux response. The entire sampler device is fabricated on a 2 mm × 2 mm chip and can be scanned over macroscopic planar samples. The flux noise at 4.2 K with 100 kHz repetition rate and 1 s of averaging is of order 1 mΦ0. This SQUID sampler will be useful for imaging dynamics in magnetic and superconducting materials and devices.

  View details for PubMedID 28863713

• Determining the vibrations between sensor and sample in SQUID microscopy APPLIED PHYSICS LETTERS Schiessl, D., Kirtley, J. R., Paulius, L., Rosenberg, A. J., Palmstrom, J. C., Ullah, R. R., Holland, C. M., Fung, Y. K., Ketchen, M. B., Gibson, G. W., Moler, K. A. 2016; 109 (23)

  View details for DOI 10.1063/1.4971201

  View details for Web of Science ID 000390677700030

• The response of small SQUID pickup loops to magnetic fields SUPERCONDUCTOR SCIENCE & TECHNOLOGY Kirtley, J. R., Paulius, L., Rosenberg, A. J., Palmstrom, J. C., Schiessl, D., Jermain, C. L., Gibbons, J., Holland, C. M., Fung, Y., Huber, M. E., Ketchen, M. B., Ralph, D. C., Gibson, G. W., Moler, K. A. 2016; 29 (12)

  View details for DOI 10.1088/0953-2048/29/12/124001

  View details for Web of Science ID 000404123400001

• Variation in superconducting transition temperature due to tetragonal domains in two-dimensionally doped SrTiO3 PHYSICAL REVIEW B Noad, H., Spanton, E. M., Nowack, K. C., Inoue, H., Kim, M., Merz, T. A., Bell, C., Hikita, Y., Xu, R., Liu, W., Vailionis, A., Hwang, H. Y., Moler, K. A. 2016; 94 (17)

  View details for DOI 10.1103/PhysRevB.94.174516

  View details for Web of Science ID 000388815300010

• Ultrathin two-dimensional superconductivity with strong spin-orbit coupling PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Nam, H., Chen, H., Liu, T., Kim, J., Zhang, C., Yong, J., Lemberger, T. R., Kratz, P. A., Kirtley, J. R., Moler, K., Adams, P. W., MacDonald, A. H., Shih, C. 2016; 113 (38): 10513-10517

  Abstract

  We report on a study of epitaxially grown ultrathin Pb films that are only a few atoms thick and have parallel critical magnetic fields much higher than the expected limit set by the interaction of electron spins with a magnetic field, that is, the Clogston-Chandrasekhar limit. The epitaxial thin films are classified as dirty-limit superconductors because their mean-free paths, which are limited by surface scattering, are smaller than their superconducting coherence lengths. The uniformity of superconductivity in these thin films is established by comparing scanning tunneling spectroscopy, scanning superconducting quantum interference device (SQUID) magnetometry, double-coil mutual inductance, and magneto-transport, data that provide average superfluid rigidity on length scales covering the range from microscopic to macroscopic. We argue that the survival of superconductivity at Zeeman energies much larger than the superconducting gap can be understood only as the consequence of strong spin-orbit coupling that, together with substrate-induced inversion-symmetry breaking, produces spin splitting in the normal-state energy bands that is much larger than the superconductor's energy gap.

  View details for DOI 10.1073/pnas.1611967113

  View details for PubMedID 27601678

• Scanning SQUID susceptometers with sub-micron spatial resolution REVIEW OF SCIENTIFIC INSTRUMENTS Kirtley, J. R., Paulius, L., Rosenberg, A. J., Palmstrom, J. C., Holland, C. M., Spanton, E. M., Schiessl, D., Jermain, C. L., Gibbons, J., Fung, Y. K., Huber, M. E., Ralph, D. C., Ketchen, M. B., Gibson, G. W., Moler, K. A. 2016; 87 (9)

  Abstract

  Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ0/Hz(1/2). This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes the spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.

  View details for DOI 10.1063/1.4961982

  View details for Web of Science ID 000385634500029

  View details for PubMedID 27782557

• Edge transport in the trivial phase of InAs/GaSb NEW JOURNAL OF PHYSICS Nichele, F., Suominen, H. J., Kjaergaard, M., Marcus, C. M., Sajadi, E., Folk, J. A., Qu, F., Beukman, A. J., de Vries, F. K., van Veen, J., Nadj-Perge, S., Kouwenhoven, L. P., Binh-Minh Nguyen, B. M., Kiselev, A. A., Yi, W., Sokolich, M., Manfra, M. J., Spanton, E. M., Moler, K. A. 2016; 18

  View details for DOI 10.1088/1367-2630/18/8/083005

  View details for Web of Science ID 000388580400001

• Magnetic coupling at rare earth ferromagnet/transition metal ferromagnet interfaces: A comprehensive study of Gd/Ni SCIENTIFIC REPORTS Higgs, T. D., Bonetti, S., Ohldag, H., Banerjee, N., Wang, X. L., Rosenberg, A. J., Cai, Z., Zhao, J. H., Moler, K. A., Robinson, J. W. 2016; 6

  Abstract

  Thin film magnetic heterostructures with competing interfacial coupling and Zeeman energy provide a fertile ground to study phase transition between different equilibrium states as a function of external magnetic field and temperature. A rare-earth (RE)/transition metal (TM) ferromagnetic multilayer is a classic example where the magnetic state is determined by a competition between the Zeeman energy and antiferromagnetic interfacial exchange coupling energy. Technologically, such structures offer the possibility to engineer the macroscopic magnetic response by tuning the microscopic interactions between the layers. We have performed an exhaustive study of nickel/gadolinium as a model system for understanding RE/TM multilayers using the element-specific measurement technique x-ray magnetic circular dichroism, and determined the full magnetic state diagrams as a function of temperature and magnetic layer thickness. We compare our results to a modified Stoner-Wohlfarth-based model and provide evidence of a thickness-dependent transition to a magnetic fan state which is critical in understanding magnetoresistance effects in RE/TM systems. The results provide important insight for spintronics and superconducting spintronics where engineering tunable magnetic inhomogeneity is key for certain applications.

  View details for DOI 10.1038/srep30092

  View details for Web of Science ID 000380027100001

  View details for PubMedID 27444683

  View details for PubMedCentralID PMC4957098

• Depth resolved domain mapping in tetragonal SrTiO3 by micro-Laue diffraction APPLIED PHYSICS LETTERS Merz, T. A., Noad, H., Xu, R., Inoue, H., Liu, W., Hikita, Y., Vailionis, A., Moler, K. A., Hwang, H. Y. 2016; 108 (18)

  View details for DOI 10.1063/1.4948351

  View details for Web of Science ID 000377023300026

• TOPOLOGICAL MATTER Observation of chiral currents at the magnetic domain boundary of a topological insulator SCIENCE Wang, Y. H., Kirtley, J. R., Katmis, F., Jarillo-Herrero, P., Moodera, J. S., Moler, K. A. 2015; 349 (6251): 948-952

  Abstract

  A magnetic domain boundary on the surface of a three-dimensional topological insulator is predicted to host a chiral edge state, but direct demonstration is challenging. We used a scanning superconducting quantum interference device to show that current in a magnetized topological insulator heterostructure (EuS/Bi2Se3) flows at the edge when the Fermi level is gate-tuned to the surface band gap. We further induced micrometer-scale magnetic structures on the heterostructure and detected a chiral edge current at the magnetic domain boundary. The chirality of the current was determined by magnetization of the surrounding domain, and its magnitude by the local chemical potential rather than the applied current. Such magnetic structures provide a platform for detecting topological magnetoelectric effects and may enable progress in quantum information processing and spintronics.

  View details for DOI 10.1126/science.aaa0508

  View details for Web of Science ID 000360646800046

• Nonsinusoidal Current-Phase Relationship in Josephson Junctions from the 3D Topological Insulator HgTe. Physical review letters Sochnikov, I., Maier, L., Watson, C. A., Kirtley, J. R., Gould, C., Tkachov, G., Hankiewicz, E. M., Brüne, C., Buhmann, H., Molenkamp, L. W., Moler, K. A. 2015; 114 (6): 066801-?

  Abstract

  We use superconducting quantum interference device microscopy to characterize the current-phase relation (CPR) of Josephson junctions from the three-dimensional topological insulator HgTe (3D HgTe). We find clear skewness in the CPRs of HgTe junctions ranging in length from 200 to 600 nm. The skewness indicates that the Josephson current is predominantly carried by Andreev bound states with high transmittance, and the fact that the skewness persists in junctions that are longer than the mean free path suggests that the effect may be related to the helical nature of the Andreev bound states in the surface of HgTe. These experimental results suggest that the topological properties of the normal state can be inherited by the induced superconducting state, and that 3D HgTe is a promising material for realizing the many exciting proposals that require a topological superconductor.

  View details for PubMedID 25723235

• Nonsinusoidal Current-Phase Relationship in Josephson Junctions from the 3D Topological Insulator HgTe PHYSICAL REVIEW LETTERS Sochnikov, I., Maier, L., Watson, C. A., Kirtley, J. R., Gould, C., Tkachov, G., Hankiewicz, E. M., Bruene, C., Buhmann, H., Molenkamp, L. W., Moler, K. A. 2015; 114 (6)

  Abstract

  We use superconducting quantum interference device microscopy to characterize the current-phase relation (CPR) of Josephson junctions from the three-dimensional topological insulator HgTe (3D HgTe). We find clear skewness in the CPRs of HgTe junctions ranging in length from 200 to 600 nm. The skewness indicates that the Josephson current is predominantly carried by Andreev bound states with high transmittance, and the fact that the skewness persists in junctions that are longer than the mean free path suggests that the effect may be related to the helical nature of the Andreev bound states in the surface of HgTe. These experimental results suggest that the topological properties of the normal state can be inherited by the induced superconducting state, and that 3D HgTe is a promising material for realizing the many exciting proposals that require a topological superconductor.

  View details for DOI 10.1103/PhysRevLett.114.066801

  View details for Web of Science ID 000350244900012

• Images of Edge Current in InAs/GaSb Quantum Wells. Physical review letters Spanton, E. M., Nowack, K. C., Du, L., Sullivan, G., Du, R., Moler, K. A. 2014; 113 (2): 026804-?

  Abstract

  Quantum spin Hall devices with edges much longer than several microns do not display ballistic transport; that is, their measured conductances are much less than e^{2}/h per edge. We imaged edge currents in InAs/GaSb quantum wells with long edges and determined an effective edge resistance. Surprisingly, although the effective edge resistance is much greater than h/e^{2}, it is independent of temperature up to 30 K within experimental resolution. Known candidate scattering mechanisms do not explain our observation of an effective edge resistance that is large yet temperature independent.

  View details for PubMedID 25062220

• Direct measurement of internal magnetic fields in natural sands using scanning SQUID microscopy. Journal of magnetic resonance Walbrecker, J. O., Kalisky, B., Grombacher, D., Kirtley, J., Moler, K. A., Knight, R. 2014; 242: 10-17

  Abstract

  NMR experiments are ideally carried out in well-controlled magnetic fields. When samples of natural porous materials are studied, the situation can be complicated if the sample itself contains magnetic components, giving rise to internal magnetic fields in the pore space that modulate the externally applied fields. If not properly accounted for, the internal fields can lead to misinterpretation of relaxation, diffusion, or imaging data. To predict the potential effect of internal fields, and develop effective mitigation strategies, it is important to develop a quantitative understanding of the magnitude and distribution of internal fields occurring in natural porous media. To develop such understanding, we employ scanning SQUID microscopy, a technique that can detect magnetic field variations very accurately at high spatial resolution (∼3μm). We prepared samples from natural unconsolidated aquifer material, and scanned areas of about 200×200μm in a very low background magnetic field of ∼2μT. We found large amplitude variations with a magnitude of about 2mT, across a relatively long spatial scale of about 200μm, that are associated with a large magnetic grain (>50μm radius) with a strong magnetic remanence. We also detected substantial variations exceeding 60μT on small spatial scales of about ∼10μm. We attribute these small-scale variations to very fine-grained magnetic material. Because we made our measurements at very low background field, the observed variations are not induced by the background field but due to magnetic remanence. Consequently, the observed internal fields will affect even low-field NMR experiments.

  View details for DOI 10.1016/j.jmr.2014.01.012

  View details for PubMedID 24589519

• Locally enhanced conductivity due to the tetragonal domain structure in LaAlO3/SrTiO3 heterointerfaces. Nature materials Kalisky, B., Spanton, E. M., Noad, H., Kirtley, J. R., Nowack, K. C., Bell, C., Sato, H. K., Hosoda, M., Xie, Y., Hikita, Y., Woltmann, C., Pfanzelt, G., Jany, R., Richter, C., Hwang, H. Y., Mannhart, J., Moler, K. A. 2013; 12 (12): 1091-1095

  Abstract

  The ability to control materials properties through interface engineering is demonstrated by the appearance of conductivity at the interface of certain insulators, most famously the {001} interface of the band insulators LaAlO3 and TiO2-terminated SrTiO3 (STO; refs , ). Transport and other measurements in this system show a plethora of diverse physical phenomena. To better understand the interface conductivity, we used scanning superconducting quantum interference device microscopy to image the magnetic field locally generated by current in an interface. At low temperature, we found that the current flowed in conductive narrow paths oriented along the crystallographic axes, embedded in a less conductive background. The configuration of these paths changed on thermal cycling above the STO cubic-to-tetragonal structural transition temperature, implying that the local conductivity is strongly modified by the STO tetragonal domain structure. The interplay between substrate domains and the interface provides an additional mechanism for understanding and controlling the behaviour of heterostructures.

  View details for DOI 10.1038/nmat3753

  View details for PubMedID 24013791

• Imaging currents in HgTe quantum wells in the quantum spin Hall regime. Nature materials Nowack, K. C., Spanton, E. M., Baenninger, M., König, M., Kirtley, J. R., Kalisky, B., Ames, C., Leubner, P., Brüne, C., Buhmann, H., Molenkamp, L. W., Goldhaber-Gordon, D., Moler, K. A. 2013; 12 (9): 787-791

  Abstract

  The quantum spin Hall (QSH) state is a state of matter characterized by a non-trivial topology of its band structure, and associated conducting edge channels. The QSH state was predicted and experimentally demonstrated to be realized in HgTe quantum wells. The existence of the edge channels has been inferred from local and non-local transport measurements in sufficiently small devices. Here we directly confirm the existence of the edge channels by imaging the magnetic fields produced by current flowing in large Hall bars made from HgTe quantum wells. These images distinguish between current that passes through each edge and the bulk. On tuning the bulk conductivity by gating or raising the temperature, we observe a regime in which the edge channels clearly coexist with the conducting bulk, providing input to the question of how ballistic transport may be limited in the edge channels. Our results represent a versatile method for characterization of new QSH materials systems.

  View details for DOI 10.1038/nmat3682

  View details for PubMedID 23770727

• Imaging currents in HgTe quantum wells in the quantum spin Hall regime. Nature materials Nowack, K. C., Spanton, E. M., Baenninger, M., König, M., Kirtley, J. R., Kalisky, B., Ames, C., Leubner, P., Brüne, C., Buhmann, H., Molenkamp, L. W., Goldhaber-Gordon, D., Moler, K. A. 2013; 12 (9): 787-791

  Abstract

  The quantum spin Hall (QSH) state is a state of matter characterized by a non-trivial topology of its band structure, and associated conducting edge channels. The QSH state was predicted and experimentally demonstrated to be realized in HgTe quantum wells. The existence of the edge channels has been inferred from local and non-local transport measurements in sufficiently small devices. Here we directly confirm the existence of the edge channels by imaging the magnetic fields produced by current flowing in large Hall bars made from HgTe quantum wells. These images distinguish between current that passes through each edge and the bulk. On tuning the bulk conductivity by gating or raising the temperature, we observe a regime in which the edge channels clearly coexist with the conducting bulk, providing input to the question of how ballistic transport may be limited in the edge channels. Our results represent a versatile method for characterization of new QSH materials systems.

  View details for DOI 10.1038/nmat3682

  View details for PubMedID 23770727

• Direct measurement of current-phase relations in superconductor/topological insulator/superconductor junctions. Nano letters Sochnikov, I., Bestwick, A. J., Williams, J. R., Lippman, T. M., Fisher, I. R., Goldhaber-Gordon, D., Kirtley, J. R., Moler, K. A. 2013; 13 (7): 3086-3092

  Abstract

  Proximity to a superconductor is predicted to induce exotic quantum phases in topological insulators. Here, scanning superconducting quantum interference device (SQUID) microscopy reveals that aluminum superconducting rings with topologically insulating Bi2Se3 junctions exhibit a conventional, nearly sinusoidal 2π-periodic current-phase relations. Pearl vortices occur in longer junctions, indicating suppressed superconductivity in aluminum, probably due to a proximity effect. Our observations establish scanning SQUID as a general tool for characterizing proximity effects and for measuring current-phase relations in new materials systems.

  View details for DOI 10.1021/nl400997k

  View details for PubMedID 23795666

• Direct Measurement of Current-Phase Relations in Superconductor/Topological Insulator/Superconductor Junctions NANO LETTERS Sochnikov, I., Bestwick, A. J., Williams, J. R., Lippman, T. M., Fisher, I. R., Godhaber-Gordon, D., Kirtley, J. R., Moler, K. A. 2013; 13 (7): 3086-3092

  Abstract

  Proximity to a superconductor is predicted to induce exotic quantum phases in topological insulators. Here, scanning superconducting quantum interference device (SQUID) microscopy reveals that aluminum superconducting rings with topologically insulating Bi2Se3 junctions exhibit a conventional, nearly sinusoidal 2π-periodic current-phase relations. Pearl vortices occur in longer junctions, indicating suppressed superconductivity in aluminum, probably due to a proximity effect. Our observations establish scanning SQUID as a general tool for characterizing proximity effects and for measuring current-phase relations in new materials systems.

  View details for DOI 10.1021/nl400997k

  View details for Web of Science ID 000321884300014

• Advanced sensors for scanning SQUID microscopy IEEE 14th International Superconductive Electronics Conference (ISEC) Kirtley, J. R., Gibson, G. W., Fung, Y. K., KLOPFER, B., Nowack, K., Kratz, P. A., Mol, J., Arpes, J., Forooghi, F., Huber, M. E., Bluhm, H., Moler, K. A. IEEE. 2013

  View details for Web of Science ID 000333277300005

• Agreement between local and global measurements of the London penetration depth PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Lippman, T. M., Kalisky, B., Kim, H., Tanatar, M. A., Bud'ko, S. L., Canfield, P. C., Prozorov, R., Moler, K. A. 2012; 483: 91-93

  View details for DOI 10.1016/j.physc.2012.08.001

  View details for Web of Science ID 000311348800020

• Gate-tuned superfluid density at the superconducting LaAlO3/SrTiO3 interface PHYSICAL REVIEW B Bert, J. A., Nowack, K. C., Kalisky, B., Noad, H., Kirtley, J. R., Bell, C., Sato, H. K., Hosoda, M., Hikita, Y., Hwang, H. Y., Moler, K. A. 2012; 86 (6)

  View details for DOI 10.1103/PhysRevB.86.060503

  View details for Web of Science ID 000307271400001

• Scanning Probe Manipulation of Magnetism at the LaAlO3/SrTiO3 Heterointerface NANO LETTERS Kalisky, B., Bert, J. A., Bell, C., Xie, Y., Sato, H. K., Hosoda, M., Hikita, Y., Hwang, H. Y., Moler, K. A. 2012; 12 (8): 4055-4059

  Abstract

  Manipulation of magnetism is a longstanding goal of research in exotic materials. In this work, we demonstrate that the small ferromagnetic patches in LaAlO(3)/SrTiO(3) heterostructures can be dramatically changed by in situ contact of a scanning probe. Our results provide a platform for manipulation of small magnets through either a strong magneto-elastic coupling or sensitivity to surface modification. The ability to locally control magnetism is particularly interesting due to the presence of superconductivity with strong spin-orbit coupling in LaAlO(3)/SrTiO(3).

  View details for DOI 10.1021/nl301451e

  View details for Web of Science ID 000307211000030

  View details for PubMedID 22769056

• Scanning SQUID susceptometry of a paramagnetic superconductor PHYSICAL REVIEW B Kirtley, J. R., Kalisky, B., Bert, J. A., Bell, C., Kim, M., Hikita, Y., Hwang, H. Y., Ngai, J. H., Segal, Y., Walker, F. J., Ahn, C. H., Moler, K. A. 2012; 85 (22)

  View details for DOI 10.1103/PhysRevB.85.224518

  View details for Web of Science ID 000305531200005

• Critical thickness for ferromagnetism in LaAlO3/SrTiO3 heterostructures NATURE COMMUNICATIONS Kalisky, B., Bert, J. A., Klopfer, B. B., Bell, C., Sato, H. K., Hosoda, M., Hikita, Y., Hwang, H. Y., Moler, K. A. 2012; 3

  Abstract

  In LaAlO(3)/SrTiO(3) heterointerfaces, charge carriers migrate from the LaAlO(3) to the interface in an electronic reconstruction. Magnetism has been observed in LaAlO(3)/SrTiO(3), but its relationship to the interface conductivity is unknown. Here we show that reconstruction is necessary, but not sufficient, for the formation of magnetism. Using scanning superconducting quantum interference device microscopy we find that magnetism appears only above a critical LaAlO(3) thickness, similar to the conductivity. We observe no change in ferromagnetism with gate voltage, and detect ferromagnetism in a non-conducting p-type sample. These observations indicate that the carriers at the interface do not need to be itinerant to generate magnetism. The ferromagnetism appears in isolated patches whose density varies greatly between samples. This inhomogeneity strongly suggests that disorder or local strain generates magnetism in a population of the interface carriers.

  View details for DOI 10.1038/ncomms1931

  View details for Web of Science ID 000306099900049

  View details for PubMedID 22735450

• Calculation of the effect of random superfluid density on the temperature dependence of the penetration depth PHYSICAL REVIEW B Lippman, T. M., Moler, K. A. 2012; 85 (10)

  View details for DOI 10.1103/PhysRevB.85.104529

  View details for Web of Science ID 000302170200009

• Fluxoid fluctuations in mesoscopic superconducting rings PHYSICAL REVIEW B Bert, J. A., Koshnick, N. C., Bluhm, H., Moler, K. A. 2011; 84 (13)

  View details for DOI 10.1103/PhysRevB.84.134523

  View details for Web of Science ID 000296289500011

• Pattern-Free Growth of Carbon Nanotube Tips for Scanning Probe Microscopy NANOSCIENCE AND NANOTECHNOLOGY LETTERS Yenilmez, E., Zhang, H., Zhang, L., Deng, Z., Moler, K. A. 2011; 3 (5): 669-673

  View details for DOI 10.1166/nnl.2011.1239

  View details for Web of Science ID 000300212000012

• Direct imaging of the coexistence of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface NATURE PHYSICS Bert, J. A., Kalisky, B., Bell, C., Kim, M., Hikita, Y., Hwang, H. Y., Moler, K. A. 2011; 7 (10): 767-771

  View details for DOI 10.1038/nphys2079

  View details for Web of Science ID 000295584200013

• Behavior of vortices near twin boundaries in underdoped Ba(Fe1-xCox)(2)As-2 PHYSICAL REVIEW B Kalisky, B., Kirtley, J. R., Analytis, J. G., Chu, J., Fisher, I. R., Moler, K. A. 2011; 83 (6)

  View details for DOI 10.1103/PhysRevB.83.064511

  View details for Web of Science ID 000287483600002

• Local Measurement of the Superfluid Density in the Pnictide Superconductor Ba(Fe1-xCox)(2)As-2 across the Superconducting Dome PHYSICAL REVIEW LETTERS Luan, L., Lippman, T. M., Hicks, C. W., Bert, J. A., Auslaender, O. M., Chu, J., Analytis, J. G., Fisher, I. R., Moler, K. A. 2011; 106 (6)

  Abstract

  We measure the penetration depth λab(T) in Ba(Fe(1-x)Co(x))(2)As(2) using local techniques that do not average over the sample. The superfluid density ρs(T) ≡ 1/λab(T)2 has three main features. First, ρs (T = 0) falls sharply on the underdoped side of the dome. Second, λab(T) is flat at low T at optimal doping, indicating fully gapped superconductivity, but varies more strongly in underdoped and overdoped samples, consistent with either a power law or a small second gap. Third, ρs (T) varies steeply near Tc for optimal and underdoping. These observations are consistent with an interplay between magnetic and superconducting phases.

  View details for DOI 10.1103/PhysRevLett.106.067001

  View details for Web of Science ID 000287135400006

  View details for PubMedID 21405485

• HIGH-TEMPERATURE SUPERCONDUCTIVITY How the cuprates hid their stripes NATURE Moler, K. A. 2010; 468 (7324): 643-644

  View details for Web of Science ID 000284836700028

  View details for PubMedID 21124446

• Limits on superconductivity-related magnetization in Sr2RuO4 and PrOs4Sb12 from scanning SQUID microscopy PHYSICAL REVIEW B Hicks, C. W., Kirtley, J. R., Lippman, T. M., Koshnick, N. C., Huber, M. E., Maeno, Y., Yuhasz, W. M., Maple, M. B., Moler, K. A. 2010; 81 (21)

  View details for DOI 10.1103/PhysRevB.81.214501

  View details for Web of Science ID 000278202100003

• Meissner response of a bulk superconductor with an embedded sheet of reduced penetration depth PHYSICAL REVIEW B Kirtley, J. R., Kalisky, B., Luan, L., Moler, K. A. 2010; 81 (18)

  View details for DOI 10.1103/PhysRevB.81.184514

  View details for Web of Science ID 000278141800093

• Stripes of increased diamagnetic susceptibility in underdoped superconducting Ba(Fe(1-x)Cox)(2)As-2 single crystals: Evidence for an enhanced superfluid density at twin boundaries PHYSICAL REVIEW B Kalisky, B., Kirtley, J. R., Analytis, J. G., Chu, J., Vailionis, A., Fisher, I. R., Moler, K. A. 2010; 81 (18)

  View details for DOI 10.1103/PhysRevB.81.184513

  View details for Web of Science ID 000278141800092

• Local measurement of the penetration depth in the pnictide superconductor Ba(Fe0.95Co0.05)(2)As-2 PHYSICAL REVIEW B Luan, L., Auslaender, O. M., Lippman, T. M., Hicks, C. W., Kalisky, B., Chu, J., Analytis, J. G., Fisher, I. R., Kirtley, J. R., Moler, K. A. 2010; 81 (10)

  View details for DOI 10.1103/PhysRevB.81.100501

  View details for Web of Science ID 000276248700020

• Sequential vortex hopping in an array of artificial pinning centers PHYSICAL REVIEW B Keay, J. C., Larson, P. R., Hobbs, K. L., Johnson, M. B., Kirtley, J. R., Auslaender, O. M., Moler, K. A. 2009; 80 (16)

  View details for DOI 10.1103/PhysRevB.80.165421

  View details for Web of Science ID 000271352100130

• Evidence for a Nodal Energy Gap in the Iron-Pnictide Superconductor LaFePO from Penetration Depth Measurements by Scanning SQUID Susceptometry PHYSICAL REVIEW LETTERS Hicks, C. W., Lippman, T. M., Huber, M. E., Analytis, J. G., Chu, J., Erickson, A. S., Fisher, I. R., Moler, K. A. 2009; 103 (12)

  Abstract

  We measure changes in the penetration depth lambda of the T_{c} approximately 6 K superconductor LaFePO. In the process, scanning SQUID susceptometry is demonstrated as a technique for accurately measuring local temperature-dependent changes in lambda, ideal for studying early or difficult-to-grow materials. lambda is found to vary linearly with temperatures from 0.36 to approximately 2 K, with a slope of 143 +/- 15 A/K, suggesting line nodes in the superconducting order parameter. The linear dependence up to approximately T_{c}/3, similar to the cuprate superconductors, indicates well-developed nodes.

  View details for DOI 10.1103/PhysRevLett.103.127003

  View details for Web of Science ID 000270139000041

  View details for PubMedID 19792454

• Spinlike Susceptibility of Metallic and Insulating Thin Films at Low Temperature PHYSICAL REVIEW LETTERS Bluhm, H., Bert, J. A., Koshnick, N. C., Huber, M. E., Moler, K. A. 2009; 103 (2)

  Abstract

  Susceptibility measurements of patterned thin films at sub-K temperatures were carried out using a scanning SQUID microscope that can resolve signals corresponding to a few hundred Bohr magnetons. Several metallic and insulating thin films, even oxide-free Au films, show a paramagnetic response with a temperature dependence that indicates unpaired spins as the origin. The observed response exhibits a measurable out-of-phase component, which implies that these spins will create 1/f-like magnetic noise. The measured spin density is consistent with recent explanations of low frequency flux noise in SQUIDs and superconducting qubits in terms of spin fluctuations, and suggests that such unexpected spins may be even more ubiquitous than already indicated by earlier measurements. Our measurements set several constraints on the nature of these spins.

  View details for DOI 10.1103/PhysRevLett.103.026805

  View details for Web of Science ID 000267887800048

  View details for PubMedID 19659233

• Magnetic force microscopy study of interlayer kinks in individual vortices in the underdoped cuprate superconductor YBa2Cu3O6+x PHYSICAL REVIEW B Luan, L., Auslaender, O. M., Bonn, D. A., Liang, R., Hardy, W. N., Moler, K. A. 2009; 79 (21)

  View details for DOI 10.1103/PhysRevB.79.214530

  View details for Web of Science ID 000267699200131

• Dynamics of single vortices in grain boundaries: I-V characteristics on the femtovolt scale APPLIED PHYSICS LETTERS Kalisky, B., Kirtley, J. R., Nowadnick, E. A., Dinner, R. B., Zeldov, E., Ariando, Wenderich, S., Hilgenkamp, H., Feldmann, D. M., Moler, K. A. 2009; 94 (20)

  View details for DOI 10.1063/1.3137164

  View details for Web of Science ID 000266342800041

• Persistent Currents in Normal Metal Rings PHYSICAL REVIEW LETTERS Bluhm, H., Koshnick, N. C., Bert, J. A., Huber, M. E., Moler, K. A. 2009; 102 (13)

  Abstract

  The authors have measured the magnetic response of 33 individual cold mesoscopic gold rings, one ring at a time. The response of some sufficiently small rings has a component that is periodic in the flux through the ring and is attributed to a persistent current. Its period is close to h/e, and its sign and amplitude vary between rings. The amplitude distribution agrees well with predictions for the typical h/e current in diffusive rings. The temperature dependence of the amplitude, measured for four rings, is also consistent with theory. These results disagree with previous measurements of three individual metal rings that showed a much larger periodic response than expected. The use of a scanning SQUID microscope enabled in situ measurements of the sensor background. A paramagnetic linear susceptibility and a poorly understood anomaly around a zero field are attributed to defect spins.

  View details for DOI 10.1103/PhysRevLett.102.136802

  View details for Web of Science ID 000264888600051

  View details for PubMedID 19392385

• Mott insulator phases and first-order melting in Bi2Sr2CaCu2O8+delta crystals with periodic surface holes PHYSICAL REVIEW B Goldberg, S., Segev, Y., Myasoedov, Y., Gutman, I., Avraham, N., Rappaport, M., Zeldov, E., Tamegai, T., Hicks, C. W., Moler, K. A. 2009; 79 (6)

  View details for DOI 10.1103/PhysRevB.79.064523

  View details for Web of Science ID 000263815600085

• Limits on the Superconducting Order Parameter in NdFeAsO1-xFy from Scanning SQUID Microscopy JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Hicks, C. W., Lippman, T. M., Huber, M. E., Ren, Z., Yang, J., Zhao, Z., Moler, K. A. 2009; 78 (1)

  View details for DOI 10.1143/JPSJ.78.013708

  View details for Web of Science ID 000263287200018

• Mechanics of individual isolated vortices in a cuprate superconductor NATURE PHYSICS Auslaender, O. M., Luan, L., Straver, E. W., Hoffman, J. E., Koshnick, N. C., Zeldov, E., Bonn, D. A., Liang, R., Hardy, W. N., Moler, K. A. 2009; 5 (1): 35-39

  View details for DOI 10.1038/NPHYS1127

  View details for Web of Science ID 000262638900015

• A terraced scanning superconducting quantum interference device susceptometer with submicron pickup loops APPLIED PHYSICS LETTERS Koshnick, N. C., Huber, M. E., Bert, J. A., Hicks, C. W., Large, J., Edwards, H., Moler, K. A. 2008; 93 (24)

  View details for DOI 10.1063/1.3046098

  View details for Web of Science ID 000261896400054

• Scanning SQUID microscopy on polycrystalline SmFeAsO0.85 and NdFeAsO0.94F0.06 JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Hicks, C. W., Lippman, T. M., Moler, K. A., Huber, M. E., Ren, Z., Zhao, Z. 2008; 77: 87-90

  View details for Web of Science ID 000208783900021

• Controlled manipulation of individual vortices in a superconductor APPLIED PHYSICS LETTERS Straver, E. W., Hoffman, J. E., Auslaender, O. M., Rugar, D., Moler, K. A. 2008; 93 (17)

  View details for DOI 10.1063/1.3000963

  View details for Web of Science ID 000260571800064

• Gradiometric micro-SQUID susceptometer for scanning measurements of mesoscopic samples REVIEW OF SCIENTIFIC INSTRUMENTS Huber, M. E., Koshnick, N. C., Bluhm, H., Archuleta, L. J., Azua, T., Bjornsson, P. G., Gardner, B. W., Halloran, S. T., Lucero, E. A., Moler, K. A. 2008; 79 (5)

  Abstract

  We have fabricated and characterized micro-SQUID susceptometers for use in low-temperature scanning probe microscopy systems. The design features the following: a 4.6 mum diameter pickup loop; an integrated field coil to apply a local field to the sample; an additional counterwound pickup-loop/field-coil pair to cancel the background signal from the applied field in the absence of the sample; modulation coils to allow setting the SQUID at its optimum bias point (independent of the applied field), and shielding and symmetry that minimizes coupling of magnetic fields into the leads and body of the SQUID. We use a SQUID series array preamplifier to obtain a system bandwidth of 1 MHz. The flux noise at 125 mK is approximately 0.25 mu Phi 0/ sqrt Hz above 10 kHz, with a value of 2.5 mu Phi 0/ sqrt Hz at 10 Hz. The nominal sensitivity to electron spins located at the center of the pickup loop is approximately 200 muB/ sqrt Hz above 10 kHz, in the white-noise frequency region.

  View details for DOI 10.1063/1.2932341

  View details for Web of Science ID 000256305400019

  View details for PubMedID 18513072

• Two-dimensional vortex behavior in highly underdoped YBa2Cu3O6+x observed by scanning Hall probe microscopy PHYSICAL REVIEW B Guikema, J. W., Bluhm, H., Bonn, D. A., Liang, R., Hardy, W. N., Moler, K. A. 2008; 77 (10)

  View details for DOI 10.1103/PhysRevB.77.104515

  View details for Web of Science ID 000254542700111

• Dissipative cryogenic filters with zero dc resistance REVIEW OF SCIENTIFIC INSTRUMENTS Bluhm, H., Moler, K. A. 2008; 79 (1)

  Abstract

  The authors designed, implemented, and tested cryogenic rf filters with zero dc resistance, based on wires with a superconducting core inside a resistive sheath. The superconducting core allows low frequency currents to pass with negligible dissipation. Signals above the cutoff frequency are dissipated in the resistive part due to their small skin depth. The filters consist of twisted wire pairs shielded with copper tape. Above approximately 1 GHz, the attenuation is exponential in omega, as typical for skin depth based rf filters. By using additional capacitors of 10 nF per line, an attenuation of at least 45 dB above 10 MHz can be obtained. Thus, one single filter stage kept at mixing chamber temperature in a dilution refrigerator is sufficient to attenuate room temperature black body radiation to levels corresponding to 10 mK above about 10 MHz.

  View details for DOI 10.1063/1.2835716

  View details for Web of Science ID 000252821800042

  View details for PubMedID 18248056

• Fluctuation superconductivity in mesoscopic aluminum rings SCIENCE Koshnick, N. C., Bluhm, H., Huber, M. E., Moler, K. A. 2007; 318 (5855): 1440-1443

  Abstract

  Fluctuations are important near phase transitions, where they can be difficult to describe quantitatively. Superconductivity in mesoscopic rings is particularly intriguing because the critical temperature is an oscillatory function of magnetic field. There is an exact theory for thermal fluctuations in one-dimensional superconducting rings, which are therefore expected to be an excellent model system. We measured the susceptibility of many rings, one ring at a time, by using a scanning superconducting quantum interference device that can isolate magnetic signals that are seven orders of magnitude smaller than applied flux. We find that the fluctuation theory describes the results and that a single parameter characterizes the ways in which the fluctuations are especially important at magnetic fields where the critical temperature is suppressed.

  View details for DOI 10.1126/science.1148758

  View details for Web of Science ID 000251246100042

  View details for PubMedID 18048686

• Moment switching in nanotube magnetic force probes NANOTECHNOLOGY Kirtley, J. R., Deng, Z., Luan, L., Yenilmez, E., Dai, H., Moler, K. A. 2007; 18 (46)

  Abstract

  Magnetic images of high density vertically recorded media using metal-coated carbon nanotube tips exhibit a doubling of the spatial frequency under some conditions (Deng et al 2004 Appl. Phys. Lett. 85 6263). Here we demonstrate that this spatial frequency doubling is due to the switching of the moment direction of the nanotube tip. This results in a signal which is proportional to the absolute value of the signal normally observed in MFM. Our modeling indicates that a significant fraction of the tip volume is involved in the observed switching, and that it should be possible to image high bit densities with nanotube magnetic force sensors.

  View details for DOI 10.1088/0957-4484/18/46/465506

  View details for Web of Science ID 000250200600013

  View details for PubMedID 21730480

• Upper limit on spontaneous supercurrents in Sr2RuO4 PHYSICAL REVIEW B Kirtley, J. R., Kallin, C., Hicks, C. W., Kim, E., Liu, Y., Moler, K. A., Maeno, Y., Nelson, K. D. 2007; 76 (1)

  View details for DOI 10.1103/PhysRevB.76.014526

  View details for Web of Science ID 000248487900124

• Enhanced current flow through meandering grain boundaries in YBa2Cu3O7-delta films APPLIED PHYSICS LETTERS Dinner, R. B., Moler, K. A., Beasley, M. R., Feldmann, D. M. 2007; 90 (21)

  View details for DOI 10.1063/1.2740610

  View details for Web of Science ID 000246775900048

• Magnetic response of mesoscopic superconducting rings with two order parameters (vol 97, art no 237002, 2006) PHYSICAL REVIEW LETTERS Bluhm, H., Koshnick, N. C., Huber, M. E., Moler, K. A. 2007; 98 (20)

  View details for DOI 10.1103/PhysRevLett.98.209902

  View details for Web of Science ID 000246624000079

• Imaging ac losses in superconducting films via scanning Hall probe microscopy PHYSICAL REVIEW B Dinner, R. B., Moler, K. A., Feldmann, D. M., Beasley, M. R. 2007; 75 (14)

  View details for DOI 10.1103/PhysRevB.75.144503

  View details for Web of Science ID 000246075100081

• Noise characteristics of 100 nm scale GaAs/AlxGa1-xAs scanning Hall probes APPLIED PHYSICS LETTERS Hicks, C. W., Luan, L., Moler, K. A., Zeldov, E., Shtrikman, H. 2007; 90 (13)

  View details for DOI 10.1063/1.2717565

  View details for Web of Science ID 000245317100115

• Magnetic response of mesoscopic superconducting rings with two order parameters PHYSICAL REVIEW LETTERS Bluhm, H., Koshnick, N. C., Huber, M. E., Moler, K. A. 2006; 97 (23)

  Abstract

  The magnetic response and fluxoid transitions of superconducting aluminum rings of various sizes, deposited under conditions likely to generate a layered structure, show good agreement with a two-order-parameter Ginzburg-Landau model. For intermediate couplings, we find metastable states that have different phase winding numbers around the ring in each of the two order parameters. Those states, previously theoretically predicted, are analogous to fractional vortices in singly connected samples with two-order-parameter superconductivity. Larger coupling locks the relative phase so that the two order parameters are only manifest in the temperature dependence of the response. With increasing proximitization, this signature gradually disappears.

  View details for DOI 10.1103/PhysRevLett.97.237002

  View details for Web of Science ID 000242708900052

  View details for PubMedID 17280232

• Power law resistivity behavior in 2D superconductors across the magnetic field-tuned superconductor-insulator transition EUROPHYSICS LETTERS Sambandamurthy, G., Johansson, A., Peled, E., Shahar, D., Bjoernsson, P. G., Moler, K. A. 2006; 75 (4): 611-617

  View details for DOI 10.1209/epl/i2006-10152-3

  View details for Web of Science ID 000239503200015

• Nanotube manipulation with focused ion beam APPLIED PHYSICS LETTERS Deng, Z. F., Yenilmez, E., Reilein, A., Leu, J., DAI, H. J., Moler, K. A. 2006; 88 (2)

  View details for DOI 10.1063/1.2161395

  View details for Web of Science ID 000234606900073

• Scanning Hall probe imaging of ErNi2B2C PHYSICAL REVIEW B Bluhm, H., Sebastian, S. E., Guikema, J. W., Fisher, I. R., Moler, K. A. 2006; 73 (1)

  View details for DOI 10.1103/PhysRevB.73.014514

  View details for Web of Science ID 000235009000114

• Cryogenic scanning Hall-probe microscope with centimeter scan range and submicron resolution REVIEW OF SCIENTIFIC INSTRUMENTS Dinner, R. B., Beasley, M. R., Moler, K. A. 2005; 76 (10)

  View details for DOI 10.1063/1.2072438

  View details for Web of Science ID 000232855900013

• Scanning magnetic imaging of Sr2RuO4 PHYSICAL REVIEW B Bjornsson, P. G., Maeno, Y., Huber, M. E., Moler, K. A. 2005; 72 (1)

  View details for DOI 10.1103/PhysRevB.72.012504

  View details for Web of Science ID 000230889800033

• Metal-coated carbon nanotube tips for magnetic force microscopy APPLIED PHYSICS LETTERS Deng, Z. F., Yenilmez, E., Leu, J., Hoffman, J. E., Straver, E. W., DAI, H. J., Moler, K. A. 2004; 85 (25): 6263-6265

  View details for DOI 10.1063/1.1842374

  View details for Web of Science ID 000225769000061

• A scanning SQUID microscope in a dilution refrigerator 23rd International Conference on Low Temperature Physics (LT23) Bjornsson, P. G., Huber, M. E., Moler, K. A. ELSEVIER SCIENCE BV. 2003: 1491–1492

  View details for DOI 10.1016/S0921-4526(02)02405-5

  View details for Web of Science ID 000183802700496

• Vortex-antivortex annihilation in underdoped YBa2Cu3O6.354 23rd International Conference on Low Temperature Physics (LT23) Gardner, B. W., Wynn, J. C., Bonn, D. A., Liang, R. X., Hardy, W. N., Moler, K. A. ELSEVIER SCIENCE BV. 2003: 725–726

  View details for DOI 10.1016/S0921-4534(02)02515-7

  View details for Web of Science ID 000183340300353

• Preparation and characterization of homogeneous YBCO single crystals with doping level near the SC-AFM boundary PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Liang, R., Bonn, D. A., Hardy, W. N., Wynn, J. C., Moler, K. A., Lu, L., LaRochelle, S., Zhou, L., Greven, M., Lurio, L., Mochrie, S. G. 2002; 383 (1-2): 1-7

  View details for Web of Science ID 000179355700001

• Manipulation of single vortices in YBa2Cu3O6.354 with a locally applied magnetic field APPLIED PHYSICS LETTERS Gardner, B. W., Wynn, J. C., Bonn, D. A., Liang, R. X., Hardy, W. N., Kirtley, J. R., Kogan, V. G., Moler, K. A. 2002; 80 (6): 1010-1012

  View details for Web of Science ID 000173612900036

• A limit on spin-charge separation in high-T-c superconductors from the absence of a vortex-memory effect NATURE Bonn, D. A., Wynn, J. C., Gardner, B. W., Lin, Y. J., Liang, R., Hardy, W. N., Kirtley, J. R., Moler, K. A. 2001; 414 (6866): 887-889

  Abstract

  There is a long-standing debate about whether spin-charge separation is the root cause of the peculiar normal-state properties and high superconducting transition temperatures of the high-Tc materials. In the proposed state of matter, the elementary excitations are not electron-like, as in conventional metals, but rather the electron 'fractionalizes' to give excitations that are chargeless spin-1/2 fermions (spinons) and charge +e bosons (chargons). Although spin-charge separation has been well established in one dimension, the theoretical situation for two dimensions is controversial and experimental evidence for it in the high-Tc materials is indirect. A model with sharp experimental tests for a particular type of separation in two dimensions has recently been proposed. Here we report the results of those experimental tests, placing a conservative upper limit of 190 K on the energy of the proposed topological defects known as visons. There is still debate about the extent to which this experiment can settle the issue of spin-charge separation in the high-Tc copper oxides, because some forms of the separation are able to avoid the need for visons. But at least one class of theories that all predict a vortex-memory effect now are unlikely models for the copper oxides.

  View details for Web of Science ID 000172813300039

  View details for PubMedID 11780056

• Limits on spin-charge separation from h/2e fluxoids in very underdoped YBa2Cu3O6+x PHYSICAL REVIEW LETTERS Wynn, J. C., Bonn, D. A., Gardner, B. W., Lin, Y. J., Liang, R. X., Hardy, W. N., Kirtley, J. R., Moler, K. A. 2001; 87 (19)

  Abstract

  Magnetic flux in superconductors is usually quantized in units of h/2e. Here we report scanning SQUID and scanning Hall probe studies of single fluxoids in high purity YBa2Cu3O6.35 crystals (T(c) less, similar 13 K), extending flux quantization studies to a region of the cuprate phase diagram where the superfluid density is sufficiently low that novel behavior has been predicted. Some scenarios in which superconductivity results from spin-charge separation predict h/e fluxoids in materials with low superfluid density. Our observations of only h/2e fluxoids set limits on these theories.

  View details for DOI 10.1103/PhysRevLett.87.197002

  View details for Web of Science ID 000172027200047

  View details for PubMedID 11690445

• Scanning superconducting quantum interference device microscope in a dilution refrigerator REVIEW OF SCIENTIFIC INSTRUMENTS Bjornsson, P. G., Gardner, B. W., Kirtley, J. R., Moler, K. A. 2001; 72 (11): 4153-4158

  View details for Web of Science ID 000171797000017

• Scanning superconducting quantum interference device susceptometry REVIEW OF SCIENTIFIC INSTRUMENTS Gardner, B. W., Wynn, J. C., Bjornsson, P. G., Straver, E. W., Moler, K. A., Kirtley, J. R., Ketchen, M. B. 2001; 72 (5): 2361-2364

  View details for Web of Science ID 000168254300022

• Images of interlayer Josephson vortices in single-layer cuprates International Conference on Materials and Mechanisms of Superconductivity High Temperature Superconductors VI Moler, K. A., Kirtley, J. R., Liang, R. X., Bonn, D. A., Hardy, W. N., Williams, J. M., Schlueter, J. A., Hinks, D., Villard, G., Maignan, A., Nohara, M., Takagi, H. ELSEVIER SCIENCE BV. 2000: 977–980

  View details for Web of Science ID 000165855700103

• Temperature Dependence of the Half-Integer Magnetic Flux Quantum. Science (New York, N.Y.) Kirtley, J. R., Tsuei, C. C., Moler, K. A. 1999; 285 (5432): 1373-1375

  Abstract

  The temperature dependence of the half-integer magnetic flux quantum effect in thin-film tricrystal samples of the high-critical-temperature cuprate superconductor YBa(2)Cu(3)O(7-delta) was measured and found to persist from a temperature of 0.5 kelvin through a critical temperature of about 90 kelvin, with no change in total flux. This result implies that d-wave symmetry pairing predominates in this cuprate, with a small component of time-reversal symmetry breaking, if any, over the entire temperature range.

  View details for PubMedID 10464089

• Temperature dependence of the half-integer magnetic flux quantum SCIENCE Kirtley, J. R., Tsuei, C. C., Moler, K. A. 1999; 285 (5432): 1373-1375

  Abstract

  The temperature dependence of the half-integer magnetic flux quantum effect in thin-film tricrystal samples of the high-critical-temperature cuprate superconductor YBa(2)Cu(3)O(7-delta) was measured and found to persist from a temperature of 0.5 kelvin through a critical temperature of about 90 kelvin, with no change in total flux. This result implies that d-wave symmetry pairing predominates in this cuprate, with a small component of time-reversal symmetry breaking, if any, over the entire temperature range.

  View details for Web of Science ID 000082233500033

• Variable sample temperature scanning superconducting quantum interference device microscope APPLIED PHYSICS LETTERS Kirtley, J. R., Tsuei, C. C., Moler, K. A., Kogan, V. G., Clem, J. R., Turberfield, A. J. 1999; 74 (26): 4011-4013

  View details for Web of Science ID 000080994200031

• Inhomogeneous interlayer Josephson coupling in kappa-(BEDT-TTF)(2)Cu(NCS)(2) JOURNAL OF PHYSICS-CONDENSED MATTER Kirtley, J. R., Moler, K. A., Schlueter, J. A., Williams, J. M. 1999; 11 (8): 2007-2016

  View details for Web of Science ID 000079096800013

• Magnetic field of an in-plane vortex outside a layered superconductor PHYSICAL REVIEW B Kirtley, J. R., Kogan, V. G., Clem, J. R., Moler, K. A. 1999; 59 (6): 4343-4348

  View details for Web of Science ID 000078699400055

• The influence of grain boundary roughness on tricrystal symmetry tests NATO Advanced Research Workshop on Symmetry and Pairing in Superconductors Kirtley, J. R., Tsuei, C. C., Moler, K. A., Mannhart, J., Hilgenkamp, H. SPRINGER. 1999: 337–346

  View details for Web of Science ID 000079306800030

• c-axis penetration depth in single crystal La2-xSrxCuO4 Conference on High Temperature Superconductivity Kirtley, J. R., Moler, K. A., Nohara, M., Takagi, H. AMER INST PHYSICS. 1999: 247–252

  View details for Web of Science ID 000083461600043

• Global and local measures of the intrinsic Josephson coupling in Tl2Ba2CuO6 as a test of the interlayer tunnelling model NATURE Tsvetkov, A. A., van der Marel, D., Moler, K. A., Kirtley, J. R., de Boer, J. L., Meetsma, A., Ren, Z. F., Koleshnikov, N., Dulic, D., Damascelli, A., Gruninger, M., Schutzmann, J., van der Eb, J. W., Somal, H. S., Wang, J. H. 1998; 395 (6700): 360-362

  View details for Web of Science ID 000076083800046

• c-Axis penetration depth of Hg-1201 single crystals PHYSICAL REVIEW LETTERS Kirtley, J. R., Moler, K. A., Villard, G., Maignan, A. 1998; 81 (10): 2140-2143

  View details for Web of Science ID 000075682400039

• Images of interlayer Josephson vortices in Tl2Ba2CuO6+delta SCIENCE Moler, K. A., Kirtley, J. R., Hinks, D. G., Li, T. W., Xu, M. 1998; 279 (5354): 1193-1196

  Abstract

  The strength of the interlayer Josephson tunneling in layered superconductors is an essential test of the interlayer tunneling model as a mechanism for superconductivity, as well as a useful phenomenological parameter. A scanning superconducting quantum interference device (SQUID) microscope was used to image interlayer Josephson vortices in Tl2Ba2CuO6+delta and to obtain a direct measure of the interlayer tunneling in a high-transition temperature superconductor with a single copper oxide plane per unit cell. The measured interlayer penetration depth, lambdac, is approximately 20 micrometers, about 20 times the penetration depth required by the interlayer tunneling model.

  View details for Web of Science ID 000072115200038

• Flux quantization experiments in cuprate superconductors NATO Advanced Study Institute on the Gap Symmetry and Fluctuations in High-T(c) Superconductors Kirtley, J. R., Tsuei, C. C., Moler, K. A. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1998: 537–556

  View details for Web of Science ID 000077391900029

• Spontaneous flux and magnetic-interference patterns in O-pi Josephson junctions PHYSICAL REVIEW B Kirtley, J. R., Moler, K. A., Scalapino, D. J. 1997; 56 (2): 886-891

  View details for Web of Science ID A1997XL82700057

• Influence of d(x2-y2) symmetry on device applications of high-T-c grain boundary junctions 1996 Applied Superconductivity Conference Hilgenkamp, H., Mannhart, J., Mayer, B., Gerber, C., Kirtley, J. R., Moler, K. A. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 1997: 3670–73

  View details for Web of Science ID A1997XH86700342

• Scanning SQUID microscopy of sparsely twinned YBa2Cu3O7-delta PHYSICAL REVIEW B Moler, K. A., Kirtley, J. R., Liang, R. X., Bonn, D., Hardy, W. N. 1997; 55 (18): 12753-12758

  View details for Web of Science ID A1997XA26000107

• Specific heat of YBa2Cu3O7-delta PHYSICAL REVIEW B Moler, K. A., Sisson, D. L., Urbach, J. S., Beasley, M. R., Kapitulnik, A., BAAR, D. J., Liang, R. X., Hardy, W. N. 1997; 55 (6): 3954-3965

  View details for Web of Science ID A1997WJ87500091

• Generation of magnetic flux by single grain boundaries of YBa2Cu3O7-x PHYSICAL REVIEW LETTERS Mannhart, J., Hilgenkamp, H., Mayer, B., Gerber, C., Kirtley, J. R., Moler, K. A., Sigrist, M. 1996; 77 (13): 2782-2785

  View details for Web of Science ID A1996VH76700047

• Basic aspects of high-T-c grain boundary devices 2nd European Workshop on Low Temperature Electronics (WOLTE 2) Mannhart, J., Hilgenkamp, H., Mayer, B., Gerber, C., Kirtley, J. R., Moler, K. A., Sigrist, M. EDP SCIENCES S A. 1996: 329–34

  View details for Web of Science ID A1996UU97300051

• Direct imaging of integer and half-integer Josephson vortices in high-T-c grain boundaries PHYSICAL REVIEW LETTERS Kirtley, J. R., Tsuei, C. C., Rupp, M., Sun, J. Z., YUJAHNES, L. S., Gupta, A., Ketchen, M. B., Moler, K. A., Bhushan, M. 1996; 76 (8): 1336-1339

  View details for Web of Science ID A1996TV69300039

• Half-integer flux quantum effect in cuprate superconductors - A probe of pairing symmetry 15th General Conference of the Condensed Matter Division of the European-Physical-Society Tsuei, C. C., Kirtley, J. R., Gupta, A., Sun, J. Z., Moler, K. A., Ren, Z. F., Wang, J. H. IOP PUBLISHING LTD. 1996: 212–214

  View details for Web of Science ID A1996WD64300039

• Scanning SQUID microscope tests of the symmetry of the high-T-c gap 21st International Conference on Low Temperature Physics (LT 21) Kirtley, J. R., Tsuei, C. C., Moler, K. A., Sun, J. Z., Gupta, A., Ren, Z. F., Wang, J. H., Li, Z. Z., Raffy, H., Mannhart, J., Hilgenkamp, H., Mayer, B., Gerber, C. INST PHYSICS ACAD SCI CZECH REPUBLIC. 1996: 3169–3176

  View details for Web of Science ID A1996WH15200046

• Specific heat of YBa2Cu3O7-delta single crystals: Implications for the vortex structure Conference on Spectroscopies in Novel Superconductors Moler, K. A., Kapitulnik, A., BAAR, D. J., Liang, R. X., Hardy, W. N. PERGAMON-ELSEVIER SCIENCE LTD. 1995: 1899–1904

  View details for Web of Science ID A1995TL54700099

• MAGNETIC-FIELD DEPENDENCE OF THE DENSITY-OF-STATES OF YBA2CU3O6.95 - IMPLICATIONS FOR THE VORTEX STRUCTURE University-of-Miami Workshop on High-Temperature Superconductivity - Physical Properties and Mechanisms Moler, K. A., BAAR, D. J., Liang, R. X., Hardy, W. N., Kapitulnik, A. SPRINGER/PLENUM PUBLISHERS. 1995: 571–74

  View details for Web of Science ID A1995RX14100010

• PROPOSED THERMODYNAMIC METHOD TO DETERMINE THE VORTEX MASS IN LAYERED SUPERCONDUCTORS JOURNAL OF LOW TEMPERATURE PHYSICS Moler, K. A., Fetter, A. L., Kapitulnik, A. 1995; 100 (3-4): 185-193

  View details for Web of Science ID A1995RT61000002

• NORMAL-MODES AND SPECIFIC-HEAT OF AN UNDAMPED 3-DIMENSIONAL LATTICE OF PANCAKE VORTICES IN THIN SUPERCONDUCTING MULTILAYERS PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Fetter, A. L., Kapitulnik, A., Moler, K. A. 1994; 235: 1777-1778

  View details for Web of Science ID A1994QC69500118

• MAGNETIC-FIELD DEPENDENCE OF THE ELECTRONIC SPECIFIC-HEAT IN YBA2CU3O6.95 SINGLE-CRYSTALS PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Moler, K. A., BAAR, D. J., Urbach, J. S., Liang, R. X., Hardy, W. N., Kapitulnik, A. 1994; 235: 1775-1776

  View details for Web of Science ID A1994QC69500117

• MAGNETIC-FIELD DEPENDENCE OF THE DENSITY-OF-STATES OF YBA2CU3O6.95 AS DETERMINED FROM THE SPECIFIC-HEAT PHYSICAL REVIEW LETTERS Moler, K. A., BAAR, D. J., Urbach, J. S., Liang, R. X., Hardy, W. N., Kapitulnik, A. 1994; 73 (20): 2744-2747

  View details for Web of Science ID A1994PQ93200027

• THEORETICAL-ANALYSIS OF VELOCITY-SELECTIVE RAMAN TRANSITIONS PHYSICAL REVIEW A Moler, K., Weiss, D. S., Kasevich, M., Chu, S. 1992; 45 (1): 342-348

  View details for Web of Science ID A1992GY51800046

• ATOMIC VELOCITY SELECTION USING STIMULATED RAMAN TRANSITIONS PHYSICAL REVIEW LETTERS Kasevich, M., Weiss, D. S., Riis, E., Moler, K., Kasapi, S., Chu, S. 1991; 66 (18): 2297-2300

  View details for Web of Science ID A1991FK18300005

• APPLICATIONS OF LASER COOLING AND TRAPPING 12TH INTERNATIONAL CONF ON ATOMIC PHYSICS ( ICAP-12 ) Kasevich, M., Moler, K., Riis, E., SUNDERMAN, E., Weiss, D., Chu, S. AIP PRESS. 1991: 47–57

  View details for Web of Science ID A1991BU34P00003

• ATOM FUNNEL FOR THE PRODUCTION OF A SLOW, HIGH-DENSITY ATOMIC-BEAM PHYSICAL REVIEW LETTERS Riis, E., Weiss, D. S., Moler, K. A., Chu, S. 1990; 64 (14): 1658-1661

  View details for Web of Science ID A1990CW76100014