Paulina Majchrzak

All Publications

• Macroscopic Uniform 2D Moiré Superlattices with Controllable Angles. Journal of the American Chemical Society Zaborski, G., Majchrzak, P. E., Lai, S., Johnson, A. C., Li, Q., Saunders, A. P., Zhu, Z., Deng, Y., Lu, D., Hashimoto, M., Shen, Z. X., Liu, F. 2025

  Abstract

  Moiré superlattices, engineered through precise stacking of van der Waals (vdW) layers, hold immense promise for exploring strongly correlated and topological phenomena. However, these applications have been held back by the common preparation method: tear-and-stack of Scotch tape exfoliated monolayers, which suffer from low efficiency and reproducibility, twist angle inhomogeneity, interfacial contamination, and micrometer sizes. Here, we report an effective strategy to construct highly consistent mixed-dimensional and twisted bilayer vdW moiré structures with high production throughput, near-unity yield, pristine interfaces, precisely controlled twist angles, and macroscopic scale (up to centimeters) with enhanced thermal stability. We demonstrate the versatility across various vdW materials, including transition metal dichalcogenides, graphene, and hBN. The expansive size and high quality of moiré structures enable reciprocal-space high-resolution mapping of the superlattices and back-folded moiré mini band structures with low energy electron diffraction (LEED) and angle-resolved photoemission spectroscopy (ARPES). In particular, we identify the backfolded bands at the K point of twisted transition metal dichalcogenide moiré structures. This technique will have broad applications in both fundamental studies and the mass production of twistronic devices.

  View details for DOI 10.1021/jacs.5c09131

  View details for PubMedID 41060287

• Resonantly enhanced photoemission from topological surface states in MnBi6Te10. Journal of physics. Condensed matter : an Institute of Physics journal Majchrzak, P. E., Jones, A., Volckaert, K., Pan, X. C., Hofmann, P., Chen, Y. P., Miwa, J. A., Ulstrup, S. 2025

  Abstract

  The dispersion of topological surface bands in MnBi2Te4-based magnetic topological insulator heterostructures is strongly affected by band hybridization and is spatially inhomogeneous due to varying surface layer terminations on microscopic length scales. Here, we apply micro-focused angle-resolved photoemission spectroscopy with tunable photon energy from 18 to 30 eV to distinguish bulk valence and conduction bands from surface bands on the three surface terminations of MnBi6Te10. We observe a strong enhancement of photoemission intensity from the topological surface bands at the Bi O4absorption edge, which is exploited to visualize a gapless Dirac cone on the MnBi2Te4-terminated surface and varying degrees of hybridization effects in the surface bands on the two distinct Bi2Te3-terminated surfaces.

  View details for DOI 10.1088/1361-648X/ae025b

  View details for PubMedID 40897359

• Quasiparticle Gap Renormalization Driven by Internal and External Screening in a WS2 Device PHYSICAL REVIEW LETTERS Sahoo, C., Veld, Y., Jones, A. J. H., Jiang, Z., Lupi, G., Majchrzak, P. E., Hsieh, K., Watanabe, K., Taniguchi, T., Hofmann, P., Miwa, J. A., Chen, Y. P., Rosner, M., Ulstrup, S. 2025; 135 (5): 056401

  Abstract

  The electronic band gap of a two-dimensional semiconductor within a device architecture is sensitive to variations in screening properties of adjacent materials in the device and to gate-controlled doping. Here, we employ microfocused angle-resolved photoemission spectroscopy to separate band gap renormalization effects stemming from environmental screening and electron doping during in situ gating of a single-layer WS_{2} device. The WS_{2} is supported on hexagonal boron nitride and contains a section that is exposed to vacuum and another section that is encapsulated by a graphene contact. We directly observe the doping-induced semiconductor-metal transition and band gap renormalization in the two sections of WS_{2}. Surprisingly, a larger band gap renormalization is observed in the vacuum-exposed section than in the graphene-encapsulated-and thus ostensibly better screened-section of the WS_{2}. Using GW calculations, we determine that intrinsic screening due to stronger doping in vacuum-exposed WS_{2} exceeds the external environmental screening in graphene-encapsulated WS_{2}.

  View details for DOI 10.1103/yllv-5zx7

  View details for Web of Science ID 001541480800007

  View details for PubMedID 40824778

• A spatial- and angle-resolved photoemission spectroscopy beamline based on capillary optics at ASTRID2 REVIEW OF SCIENTIFIC INSTRUMENTS Jones, A. J. H., Majchrzak, P., Volckaert, K., Biswas, D., Andersen, J., Hoffmann, S. V., Jones, N. C., Jiang, Z., Chen, Y. P., Jensen, M., Stenshoj, R., Bianchi, M., Hofmann, P., Ulstrup, S., Miwa, J. A. 2025; 96 (2)

  Abstract

  Angle-resolved photoemission spectroscopy (ARPES) with spatial resolution is emerging as a powerful investigative tool for the study of operational mesoscale devices and quantum materials. Here, we introduce AU-SGM4, an extreme ultraviolet beamline based at the ASTRID2 synchrotron, which is designed around an achromatic elliptical capillary optic that focuses the synchrotron light down to a lateral beam spot size of 4 μm. The beamline offers a low photon energy range of 12-150 eV, ideal for probing detailed energy- and momentum-resolved electronic structures of materials. We utilize a custom-made piezoelectric motor system with 11 degrees of freedom for precisely moving the sample and capillary optic. We demonstrate exceptional stability in beam positioning on samples across the entire available photon energy range. To showcase the capabilities of the AU-SGM4 beamline, we present simultaneous ARPES measurements and in situ gating of a graphene device and probe the nominally inaccessible microscopic-sized domains of MnBi6Te10 to obtain the energy- and momentum-dependent dispersion for each domain.

  View details for DOI 10.1063/5.0240744

  View details for Web of Science ID 001469478000002

  View details for PubMedID 40019339

• Attosecond emission delay from atoms and molecules using multi-dimensional XUV interferometry NEW JOURNAL OF PHYSICS Wyatt, A. S., Lloyd, D. T., Chapman, R. T., Thornton, C., Majchrzak, P., Jones, A. J. H., Springate, E., O'Keeffe, K. 2024; 26 (11)

  View details for DOI 10.1088/1367-2630/ad8f5b

  View details for Web of Science ID 001362373000001

• Access to the full three-dimensional Brillouin zone with time resolution, using a new tool for pump-probe angle-resolved photoemission spectroscopy. The Review of scientific instruments Majchrzak, P., Zhang, Y., Kuibarov, A., Chapman, R., Wyatt, A., Springate, E., Borisenko, S., Buchner, B., Hofmann, P., Sanders, C. E. 2024; 95 (6)

  Abstract

  Here, we report the first time- and angle-resolved photoemission spectroscopy (TR-ARPES) with the new Fermiologics "FeSuMa" analyzer. The new experimental setup has been commissioned at the Artemis laboratory of the UK Central Laser Facility. We explain here some of the advantages of the FeSuMa for TR-ARPES and discuss how its capabilities relate to those of hemispherical analyzers and momentum microscopes. We have integrated the FeSuMa into an optimized pump-probe beamline that permits photon-energy (i.e., kz)-dependent scanning, using probe energies generated from high harmonics in a gas jet. The advantages of using the FeSuMa in this situation include the possibility of taking advantage of its "fisheye" mode of operation.

  View details for DOI 10.1063/5.0179752

  View details for PubMedID 38829212

• Programming twist angle and strain profiles in 2D materials SCIENCE Kapfer, M., Jessen, B. S., Eisele, M. E., Fu, M., Danielsen, D. R., Darlington, T. P., Moore, S. L., Finney, N. R., Marchese, A., Hsieh, V., Majchrzak, P., Jiang, Z., Biswas, D., Dudin, P., Avila, J., Watanabe, K., Taniguchi, T., Ulstrup, S., Boggild, P., Schuck, P. J., Basov, D. N., Hone, J., Dean, C. R. 2023; 381 (6658): 677-681

  View details for DOI 10.1126/science.ade9995

  View details for Web of Science ID 001167286600031