All Publications

  • The chemRIXS instrument for solution-phase resonant inelastic x-ray scattering at the linac coherent light source. The Review of scientific instruments Hoffman, D. J., Garratt, D., Bain, M., Hampton, C. Y., Poulter, B. I., Joshi, J., Coslovich, G., O'Dowd, F. P., DePonte, D. P., Reid, A. H., Shen, L., Jost, D., Bionta, M. R., Turner, J. J., Lin, M. F., Heimann, P., Moeller, S. P., Koralek, J. D., Johnson, T., Ninh, K., Almeida, R., Berges, A., Fung, S., Li, S., Pelimanni, E., Nimmrich, A., Khalil, M., Young, L., Wolf, T. J., Kunnus, K., Dakovski, G. L. 2026; 97 (8)

    Abstract

    The chemRIXS instrument at the Linac Coherent Light Source (LCLS) offers new opportunities for studying solution-phase systems with time-resolved soft x-ray spectroscopic methods such as resonant inelastic x-ray scattering (RIXS) using the recently commissioned high-repetition-rate LCLS-II x-ray free-electron laser. The orders-of-magnitude x-ray flux improvement provided by the superconducting accelerator, combined with corresponding advances in the optical laser system and the liquid-jet recirculation system, enables studies on dilute systems with high signal-to-noise compared to what was possible with the LCLS-I copper accelerator. These capabilities open up time-resolved x-ray absorption spectroscopy and RIXS to entirely new classes of samples, as well as enable the development of new soft x-ray spectroscopic methods on liquid samples. An overview of the beamline components and the first LCLS-II commissioning results is presented.

    View details for DOI 10.1063/5.0335462

    View details for PubMedID 42599147

  • Picosecond Expansion in LaAlO_{3} Resonantly Driven by Infrared-Active Phonons. Physical review letters Gollwitzer, J., Kaaret, J. Z., Suyolcu, Y. E., Khalsa, G., Fernandes, R. C., Gorobtsov, O., Buchenau, S., You, C., Higgins, J., Russell, R. S., Shao, Z., Birkhölzer, Y. A., Sato, T., Chollet, M., Coslovich, G., Brützam, M., Guguschev, C., Harter, J. W., Disa, A. S., Schlom, D. G., Benedek, N. A., Singer, A. 2025; 135 (11): 116906

    Abstract

    We investigate the ultrafast structural dynamics of LaAlO_{3} thin films driven by short mid-infrared laser pulses at 20 THz. Time-resolved x-ray diffraction reveals an immediate lattice expansion and an acoustic breathing mode of the film. First-principles theory and a spring-mass model identify the direct coupling between coherently driven infrared-active phonons and strain as the underlying mechanism. Time-resolved optical birefringence measurements confirm that the amplitude of this acoustic mode scales linearly with the pump fluence, in agreement with theory. Furthermore, time-resolved x-ray diffuse scattering indicates that THz excitation enhances crystallinity by inducing a nonthermal increase in structural symmetry originating from preexisting defects. These findings highlight the potential of a multimodal approach-combining time-resolved x-ray and optical measurements and first-principles theory-to elucidate and control structural dynamics in nanoscale materials.

    View details for DOI 10.1103/vzkw-n2bm

    View details for PubMedID 41004787

  • Revealing Parallel Inter- and Intra-ligand Charge Transfer Dynamics in [Ru(L)2(dppz)]2+ Molecular Lightswitch with N K-edge X-ray Absorption Spectroscopy. Angewandte Chemie (International ed. in English) Ryland, E. S., Yang, X., Garratt, D., Henke, W. C., Kahraman, A., Taub, M., Sachs, M., Biasin, E., Hampton, C. Y., Hoffman, D. J., Coslovich, G., Kunnus, K., Dakovski, G. L., Mara, M. W., Chen, L. X., Mulfort, K. L., Li, X., Cordones, A. A. 2025: e202509496

    Abstract

    In photoactive metal complexes the localization of photoexcited charges dictates the site of chemical reactivity, but few studies measure the charge redistribution in these systems with spatial precision. Herein, we track the inter- and intra-ligand charge transfer processes that underpin light-driven charge separation in the well-studied "molecular lightswitch" [Ru(bpy)2dppz]2+ (aqueous [RutheniumII(2,2'-bipyridine)2(dipyrido[3,2-a:2',3'-c]phenazine)]2+[Cl-]2) by probing the electronic structure of ligand nitrogen atoms in real-time using ultrafast x-ray absorption spectroscopy and first principles calculations. We confirm the localization of excited electron density on the phenazine N atoms of dppz and we newly identify two parallel electron transfer pathways to populate this state.  Sub-70 fs electron transfer to the phenazine portion of dppz is observed and attributed to intra-ligand electron transfer following Ru-to-dppz metal-to-ligand charge transfer (MLCT) excitation. This fast charge transfer was not reported in prior ultrafast studies. The slower (ca. 2 ps) charge transfer reported extensively in time-resolved optical absorption and emission studies is reassigned here to inter-ligand electron "hopping" between nearly isoenergetic ligand moieties following Ru-to-bpy MLCT excitation. The results demonstrate much faster charge separation than previously identified in this well-studied system, highlighting how extended azaacene ligand motifs promote the competitive charge transfer processes needed to drive light-driven electron transfer chemistry.

    View details for DOI 10.1002/anie.202509496

    View details for PubMedID 40638863

  • Understanding the superconductivity and charge density wave interaction through quasi-static lattice fluctuations. Proceedings of the National Academy of Sciences of the United States of America Porter, Z., Shen, L., Plumley, R., Burdet, N. G., Petsch, A. N., Wen, J., Drucker, N. C., Peng, C., Chen, X. M., Fluerasu, A., Blackburn, E., Coslovich, G., Hawthorn, D. G., Turner, J. J. 2024; 121 (50): e2412182121

    Abstract

    In unconventional superconductors, coupled charge and lattice degrees of freedom can manifest in ordered phases of matter that are intertwined. In the cuprate family, fluctuating short-range charge correlations can coalesce into a longer-range charge density wave (CDW) order which is thought to intertwine with superconductivity, yet the nature of the interaction is still poorly understood. Here, by measuring subtle lattice fluctuations in underdoped YBa2Cu3O6+y on quasi-static timescales (thousands of seconds) through X-ray photon correlation spectroscopy, we report sensitivity to both superconductivity and CDW. The atomic lattice shows remarkably faster relaxational dynamics upon approaching the superconducting transition at Tc ≈ 65 K. By tracking the momentum dependence, we show that the intermediate scattering function almost monotonically scales with the relaxation distance of atoms away from their average positions above Tc and in the presence of the CDW state, while this peculiar trend is reversed for other temperatures. These observations are consistent with an incipient CDW stabilized by local strain. This work provides insights into the crucial role of relaxational atomic fluctuations for understanding the electronic physics cuprates, which are inherently disordered due to carrier doping.

    View details for DOI 10.1073/pnas.2412182121

    View details for PubMedID 39630858

  • Orbital-selective time-domain signature of nematicity dynamics in the charge-density-wave phase of La1.65Eu0.2Sr0.15CuO4. Proceedings of the National Academy of Sciences of the United States of America Bluschke, M., Gupta, N. K., Jang, H., Husain, A. A., Lee, B., Kim, M., Na, M., Dos Remedios, B., Smit, S., Moen, P., Park, S. Y., Kim, M., Jang, D., Choi, H., Sutarto, R., Reid, A. H., Dakovski, G. L., Coslovich, G., Nguyen, Q. L., Burdet, N. G., Lin, M. F., Revcolevschi, A., Park, J. H., Geck, J., Turner, J. J., Damascelli, A., Hawthorn, D. G. 2024; 121 (23): e2400727121

    Abstract

    Understanding the interplay between charge, nematic, and structural ordering tendencies in cuprate superconductors is critical to unraveling their complex phase diagram. Using pump-probe time-resolved resonant X-ray scattering on the (0 0 1) Bragg peak at the Cu [Formula: see text] and O [Formula: see text] resonances, we investigate nonequilibrium dynamics of [Formula: see text] nematic order and its association with both charge density wave (CDW) order and lattice dynamics in La[Formula: see text]Eu[Formula: see text]Sr[Formula: see text]CuO[Formula: see text]. The orbital selectivity of the resonant X-ray scattering cross-section allows nematicity dynamics associated with the planar O 2[Formula: see text] and Cu 3[Formula: see text] states to be distinguished from the response of anisotropic lattice distortions. A direct time-domain comparison of CDW translational-symmetry breaking and nematic rotational-symmetry breaking reveals that these broken symmetries remain closely linked in the photoexcited state, consistent with the stability of CDW topological defects in the investigated pump fluence regime.

    View details for DOI 10.1073/pnas.2400727121

    View details for PubMedID 38819998

  • Ultrafast perturbation of magnetic domains by optical pumping in a ferromagnetic multilayer PHYSICAL REVIEW B Zusin, D., Iacocca, E., Le Guyader, L., Reid, A. H., Schlotter, W. F., Liu, T., Higley, D. J., Coslovich, G., Wandel, S. F., Tengdin, P. M., Patel, S. K. K., Shabalin, A., Hua, N., Hrkac, S. B., Nembach, H. T., Shaw, J. M., Montoya, S. A., Blonsky, A., Gentry, C., Hoefer, M. A., Murnane, M. M., Kapteyn, H. C., Fullerton, E. E., Shpyrko, O., Durr, H. A., Silva, T. J. 2022; 106 (14)

    View details for DOI 10.1103/PhysRevB.106.144422

    View details for Web of Science ID 000879551600002

  • Anisotropic Surface Broadening and Core Depletion during the Evolution of a Strong-Field Induced Nanoplasma. Physical review letters Bacellar, C., Chatterley, A. S., Lackner, F., Pemmaraju, C. D., Tanyag, R. M., Verma, D., Bernando, C., O'Connell, S. M., Bucher, M., Ferguson, K. R., Gorkhover, T., Coffee, R. N., Coslovich, G., Ray, D., Osipov, T., Neumark, D. M., Bostedt, C., Vilesov, A. F., Gessner, O. 2022; 129 (7): 073201

    Abstract

    Strong-field ionization of nanoscale clusters provides excellent opportunities to study the complex correlated electronic and nuclear dynamics of near-solid density plasmas. Yet, monitoring ultrafast, nanoscopic dynamics in real-time is challenging, which often complicates a direct comparison between theory and experiment. Here, near-infrared laser-induced plasma dynamics in 600nm diameter helium droplets are studied by femtosecond time-resolved x-ray coherent diffractive imaging. An anisotropic, 20nm wide surface region, defined as the range where the density lies between 10% and 90% of the core value, is established within 100fs, in qualitative agreement with theoretical predictions. At longer timescales, however, the width of this region remains largely constant while the radius of the dense plasma core shrinks at average rates of 71nm/ps along and 33nm/ps perpendicular to the laser polarization. These dynamics are not captured by previous plasma expansion models. The observations are phenomenologically described within a numerical simulation; details of the underlying physics, however, remain to be explored.

    View details for DOI 10.1103/PhysRevLett.129.073201

    View details for PubMedID 36018694

  • Enhanced charge density wave coherence in a light-quenched, high-temperature superconductor. Science (New York, N.Y.) Wandel, S., Boschini, F., da Silva Neto, E. H., Shen, L., Na, M. X., Zohar, S., Wang, Y., Welch, S. B., Seaberg, M. H., Koralek, J. D., Dakovski, G. L., Hettel, W., Lin, M., Moeller, S. P., Schlotter, W. F., Reid, A. H., Minitti, M. P., Boyle, T., He, F., Sutarto, R., Liang, R., Bonn, D., Hardy, W., Kaindl, R. A., Hawthorn, D. G., Lee, J., Kemper, A. F., Damascelli, A., Giannetti, C., Turner, J. J., Coslovich, G. 2022; 376 (6595): 860-864

    Abstract

    Superconductivity and charge density waves (CDWs) are competitive, yet coexisting, orders in cuprate superconductors. To understand their microscopic interdependence, a probe capable of discerning their interaction on its natural length and time scale is necessary. We use ultrafast resonant soft x-ray scattering to track the transient evolution of CDW correlations in YBa2Cu3O6+x after the quench of superconductivity by an infrared laser pulse. We observe a nonthermal response of the CDW order characterized by a near doubling of the correlation length within 1 picosecond of the superconducting quench. Our results are consistent with a model in which the interaction between superconductivity and CDWs manifests inhomogeneously through disruption of spatial coherence, with superconductivity playing the dominant role in stabilizing CDW topological defects, such as discommensurations.

    View details for DOI 10.1126/science.abd7213

    View details for PubMedID 35587968

  • Characterization of photoinduced normal state through charge density wave in superconducting YBa2Cu3O6.67. Science advances Jang, H., Song, S., Kihara, T., Liu, Y., Lee, S., Park, S., Kim, M., Kim, H., Coslovich, G., Nakata, S., Kubota, Y., Inoue, I., Tamasaku, K., Yabashi, M., Lee, H., Song, C., Nojiri, H., Keimer, B., Kao, C., Lee, J. 2022; 8 (6): eabk0832

    Abstract

    The normal state of high-Tc cuprates has been considered one of the essential topics in high-temperature superconductivity research. However, compared to the high magnetic field study of it, understanding a photoinduced normal state remains elusive. Here, we explore a photoinduced normal state of YBa2Cu3O6.67 through a charge density wave (CDW) with time-resolved resonant soft x-ray scattering, as well as a high magnetic field x-ray scattering. In the nonequilibrium state where people predict a quenched superconducting state based on the previous optical spectroscopies, we experimentally observed a similar analogy to the competition between superconductivity and CDW shown in the equilibrium state. We further observe that the broken pairing states in the superconducting CuO2 plane via the optical pump lead to nucleation of three-dimensional CDW precursor correlation. Ultimately, these findings provide a critical clue that the characteristics of the photoinduced normal state show a solid resemblance to those under magnetic fields in equilibrium conditions.

    View details for DOI 10.1126/sciadv.abk0832

    View details for PubMedID 35138893

  • State-resolved ultrafast charge and spin dynamics in [Co/Pd] multilayers APPLIED PHYSICS LETTERS Le Guyader, L., Higley, D. J., Pancaldi, M., Liu, T., Chen, Z., Chase, T., Granitzka, P. W., Coslovich, G., Lutman, A. A., Dakovski, G. L., Schlotter, W. F., Shafer, P., Arenholz, E., Hellwig, O., Lalieu, M. L. M., Koopmans, B., Reid, A. H., Bonetti, S., Stohr, J., Durr, H. A. 2022; 120 (3)

    View details for DOI 10.1063/5.0076953

    View details for Web of Science ID 000779205300016

  • Transient resonant Auger-Meitner spectra of photoexcited thymine. Faraday discussions Wolf, T. J., Paul, A. C., Folkestad, S. D., Myhre, R. H., Cryan, J. P., Berrah, N., Bucksbaum, P. H., Coriani, S., Coslovich, G., Feifel, R., Martinez, T. J., Moeller, S. P., Mucke, M., Obaid, R., Plekan, O., Squibb, R. J., Koch, H., Guhr, M. 2021

    Abstract

    We present the first investigation of excited state dynamics by resonant Auger-Meitner spectroscopy (also known as resonant Auger spectroscopy) using the nucleobase thymine as an example. Thymine is photoexcited in the UV and probed with X-ray photon energies at and below the oxygen K-edge. After initial photoexcitation to a pipi* excited state, thymine is known to undergo internal conversion to an npi* excited state with a strong resonance at the oxygen K-edge, red-shifted from the ground state pi* resonances of thymine (see our previous study Wolf, et al., Nat. Commun., 2017, 8, 29). We resolve and compare the Auger-Meitner electron spectra associated both with the excited state and ground state resonances, and distinguish participator and spectator decay contributions. Furthermore, we observe simultaneously with the decay of the npi* state signatures the appearance of additional resonant Auger-Meitner contributions at photon energies between the npi* state and the ground state resonances. We assign these contributions to population transfer from the npi* state to a pipi* triplet state via intersystem crossing on the picosecond timescale based on simulations of the X-ray absorption spectra in the vibrationally hot triplet state. Moreover, we identify signatures from the initially excited pipi* singlet state which we have not observed in our previous study.

    View details for DOI 10.1039/d0fd00112k

    View details for PubMedID 33566045

  • Arrival Time Monitor for Sub-10 fs Soft X-ray and 800 nm Optical Pulses Muhammad, I., Frimpong, B., Daafour, J., Xu, X., Walter, P., Wolf, T. J. A., Cryan, J. P., Glownia, J. M., Robinson, J. S., Droste, S., Coslovich, G., IEEE IEEE. 2021

    View details for Web of Science ID 000831479802212

  • High-sensitivity x-ray/optical cross-correlator for next generation free-electron lasers OPTICS EXPRESS Droste, S., Zohar, S., Shen, L., White, V. E., Diaz-Jacobo, E., Coffee, R. N., Reid, A. H., Tavella, F., Minitti, M. P., Turner, J. J., Robinson, J. S., Fry, A. R., Coslovich, G. 2020; 28 (16): 23545–53

    Abstract

    We design and realize an arrival time diagnostic for ultrashort X-ray pulses achieving unprecedented high sensitivity in the soft X-ray regime via cross-correlation with a ≈1550 nm optical laser. An interferometric detection scheme is combined with a multi-layer sample design to greatly improve the sensitivity of the measurement. We achieve up to 275% of relative signal change when exposed to 1.6 mJ/cm2 of soft X-rays at 530 eV, more than a hundred-fold improvement in sensitivity as compared to previously reported techniques. The resolution of the arrival time measurement is estimated to around 2.8 fs (rms). The demonstrated X-ray arrival time monitor paves the way for sub-10 fs-level timing jitter at high repetition rate X-ray facilities.

    View details for DOI 10.1364/OE.398048

    View details for Web of Science ID 000560931200042

    View details for PubMedID 32752349

  • Orbital dynamics during an ultrafast insulator to metal transition PHYSICAL REVIEW RESEARCH Parchenko, S., Paris, E., McNally, D., Abreu, E., Dantz, M., Bothschafter, E. M., Reid, A. H., Schlotter, W. F., Lin, M., Wandel, S. F., Coslovich, G., Zohar, S., Dakovski, G. L., Turner, J. J., Moeller, S., Tseng, Y., Radovic, M., Saathe, C., Agaaker, M., Nordgren, J. E., Johnson, S. L., Schmitt, T., Staub, U. 2020; 2 (2)

    View details for DOI 10.1103/PhysRevResearch.2.023110

    View details for Web of Science ID 000602780200010

  • Tunable isolated attosecond X-ray pulses with gigawatt peak power from a free-electron laser NATURE PHOTONICS Duris, J., Li, S., Driver, T., Champenois, E. G., MacArthur, J. P., Lutman, A. A., Zhang, Z., Rosenberger, P., Aldrich, J. W., Coffee, R., Coslovich, G., Decker, F., Glownia, J. M., Hartmann, G., Helml, W., Kamalov, A., Knurr, J., Krzywinski, J., Lin, M., Nantel, M., Natan, A., O'Neal, J., Shivaram, N., Walter, P., Wang, A., Welch, J. J., Wolf, T. J. A., Xu, J. Z., Kling, M. F., Bucksbaum, P. H., Zholents, A., Huang, Z., Cryan, J. P., Marinelli, A., Marangos, J. P. 2020; 14 (1): 30-+

    View details for DOI 10.1038/s41566-019-0549-5

    View details for Web of Science ID 000504727600007

  • Evidence for photoinduced sliding of the charge-order condensate in La1.875Ba0.125CuO4 PHYSICAL REVIEW B Mitrano, M., Lee, S., Husain, A. A., Zhu, M., Munoz, G., Sun, S., Joe, Y., Reid, A. H., Wandel, S. F., Coslovich, G., Schlotter, W., van Driel, T., Schneeloch, J., Gu, G. D., Goldenfeld, N., Abbamonte, P. 2019; 100 (20)

    View details for DOI 10.1103/PhysRevB.100.205125

    View details for Web of Science ID 000496925100004

  • Ultrafast time-resolved x-ray scattering reveals diffusive charge order dynamics in La2-x Ba x CuO4. Science advances Mitrano, M., Lee, S., Husain, A. A., Delacretaz, L., Zhu, M., de la Pena Munoz, G., Sun, S. X., Joe, Y. I., Reid, A. H., Wandel, S. F., Coslovich, G., Schlotter, W., van Driel, T., Schneeloch, J., Gu, G. D., Hartnoll, S., Goldenfeld, N., Abbamonte, P. 2019; 5 (8): eaax3346

    Abstract

    Charge order is universal among high-T c cuprates, but its relation to superconductivity is unclear. While static order competes with superconductivity, dynamic order may be favorable and even contribute to Cooper pairing. Using time-resolved resonant soft x-ray scattering at a free-electron laser, we show that the charge order in prototypical La2-x Ba x CuO4 exhibits transverse fluctuations at picosecond time scales. These sub-millielectron volt excitations propagate by Brownian-like diffusion and have an energy scale remarkably close to the superconducting T c. At sub-millielectron volt energy scales, the dynamics are governed by universal scaling laws defined by the propagation of topological defects. Our results show that charge order in La2-x Ba x CuO4 exhibits dynamics favorable to the in-plane superconducting tunneling and establish time-resolved x-rays as a means to study excitations at energy scales inaccessible to conventional scattering techniques.

    View details for DOI 10.1126/sciadv.aax3346

    View details for PubMedID 31453340

  • Evaporation of an anisotropic nanoplasma Bacellar, C., Chatterley, A. S., Lackner, F., Pemmaraju, C. D., Tanyag, R. M. P., Bernando, C., Verma, D., O'Connell, S., Bucher, M., Ferguson, K. R., Gorkhover, T., Coffee, R. N., Coslovich, G., Ray, D., Osipov, T., Neumark, D. M., Bostedt, C., Vilesov, A. F., Gessner, O. edited by Cerullo, G., Ogilvie, J., Kartner, F., Khalil, M., Li, R. E D P SCIENCES. 2019

    View details for DOI 10.1051/epjconf/201920506006

    View details for Web of Science ID 000570451400122

  • High-sensitivity X-ray Optical Cross-Correlator for Next Generation Free-Electron Lasers Droste, S., Shen, L., White, V. E., Diaz-Jacobo, E., Coffee, R., Zohar, S., Reid, A. H., Tavella, F., Minitti, M. P., Turner, J. J., Gumerlock, K. L., Fry, A. R., Coslovich, G., IEEE IEEE. 2019

    View details for Web of Science ID 000482226301138

  • Atom-specific activation in CO oxidation. The Journal of chemical physics Schreck, S., Diesen, E., LaRue, J., Ogasawara, H., Marks, K., Nordlund, D., Weston, M., Beye, M., Cavalca, F., Perakis, F., Sellberg, J., Eilert, A., Kim, K. H., Coslovich, G., Coffee, R., Krzywinski, J., Reid, A., Moeller, S., Lutman, A., Ostrom, H., Pettersson, L. G., Nilsson, A. 2018; 149 (23): 234707

    Abstract

    We report on atom-specific activation of CO oxidation on Ru(0001) via resonant X-ray excitation. We show that resonant 1s core-level excitation of atomically adsorbed oxygen in the co-adsorbed phase of CO and oxygen directly drives CO oxidation. We separate this direct resonant channel from indirectly driven oxidation via X-ray induced substrate heating. Based on density functional theory calculations, we identify the valence-excited state created by the Auger decay as the driving electronic state for direct CO oxidation. We utilized the fresh-slice multi-pulse mode at the Linac Coherent Light Source that provided time-overlapped and 30 fs delayed pairs of soft X-ray pulses and discuss the prospects of femtosecond X-ray pump X-ray spectroscopy probe, as well as X-ray two-pulse correlation measurements for fundamental investigations of chemical reactions via selective X-ray excitation.

    View details for PubMedID 30579301

  • Atom-specific activation in CO oxidation JOURNAL OF CHEMICAL PHYSICS Schreck, S., Diesen, E., LaRue, J., Ogasawara, H., Marks, K., Nordlund, D., Weston, M., Beye, M., Cavalca, F., Perakis, F., Sellberg, J., Eilert, A., Kim, K., Coslovich, G., Coffee, R., Krzywinski, J., Reid, A., Moeller, S., Lutman, A., Ostrom, H., Pettersson, L. G. M., Nilsson, A. 2018; 149 (23)

    View details for DOI 10.1063/1.5044579

    View details for Web of Science ID 000454102600024

  • Ultrafast dynamics of vibrational symmetry breaking in a charge-ordered nickelate SCIENCE ADVANCES Coslovich, G., Kemper, A. F., Behl, S., Huber, B., Bechtel, H. A., Sasagawa, T., Martin, M. C., Lanzara, A., Kaindl, R. A. 2017; 3 (11)

    View details for DOI 10.1126/sciadv.1600735

    View details for Web of Science ID 000418002000001

  • Ultrafast dynamics of vibrational symmetry breaking in a charge-ordered nickelate. Science advances Coslovich, G., Kemper, A. F., Behl, S., Huber, B., Bechtel, H. A., Sasagawa, T., Martin, M. C., Lanzara, A., Kaindl, R. A. 2017; 3 (11): e1600735

    Abstract

    The ability to probe symmetry-breaking transitions on their natural time scales is one of the key challenges in nonequilibrium physics. Stripe ordering represents an intriguing type of broken symmetry, where complex interactions result in atomic-scale lines of charge and spin density. Although phonon anomalies and periodic distortions attest the importance of electron-phonon coupling in the formation of stripe phases, a direct time-domain view of vibrational symmetry breaking is lacking. We report experiments that track the transient multi-terahertz response of the model stripe compound La1.75Sr0.25NiO4, yielding novel insight into its electronic and structural dynamics following an ultrafast optical quench. We find that although electronic carriers are immediately delocalized, the crystal symmetry remains initially frozen-as witnessed by time-delayed suppression of zone-folded Ni-O bending modes acting as a fingerprint of lattice symmetry. Longitudinal and transverse vibrations react with different speeds, indicating a strong directionality and an important role of polar interactions. The hidden complexity of electronic and structural coupling during stripe melting and formation, captured here within a single terahertz spectrum, opens new paths to understanding symmetry-breaking dynamics in solids.

    View details for DOI 10.1126/sciadv.1600735

    View details for PubMedID 29202025

    View details for PubMedCentralID PMC5706742

  • Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser REVIEW OF SCIENTIFIC INSTRUMENTS Higley, D. J., Hirsch, K., Dakovski, G. L., Jal, E., Yuan, E., Liu, T., Lutman, A. A., MacArthur, J. P., Arenholz, E., Chen, Z., Coslovich, G., Denes, P., Granitzka, P. W., Hart, P., Hoffmann, M. C., Joseph, J., Le Guyader, L., Mitra, A., Moeller, S., Ohldag, H., Seaberg, M., Shafer, P., Stoehr, J., Tsukamoto, A., Nuhn, H., Reid, A. H., Duerr, H. A., Schlotter, W. F. 2016; 87 (3)

    Abstract

    X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L(3,2)-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray magnetic circular dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature.

    View details for DOI 10.1063/1.4944410

    View details for Web of Science ID 000373713300011

    View details for PubMedID 27036761

  • Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources REVIEW OF SCIENTIFIC INSTRUMENTS Shavorskiy, A., Neppl, S., Slaughter, D. S., Cryan, J. P., Siefermann, K. R., Weise, F., Lin, M., Bacellar, C., Ziemkiewicz, M. P., Zegkinoglou, I., Fraund, M. W., Khurmi, C., Hertlein, M. P., Wright, T. W., Huse, N., Schoenlein, R. W., Tyliszczak, T., Coslovich, G., Robinson, J., Kaindl, R. A., Rude, B. S., Oelsner, A., Maehl, S., Bluhm, H., Gessner, O. 2014; 85 (9): 093102

    Abstract

    An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ~0.1 mm spatial resolution and ~150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E(p) = 150 eV and an electron kinetic energy range KE = 503-508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ~9 ns at a pass energy of 50 eV and ~1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the angular spread with the retarding ratio can be well approximated by applying Liouville's theorem of constant emittance to the electron trajectories inside the lens system. The performance of the setup is demonstrated by characterizing the laser fluence-dependent transient surface photovoltage response of a laser-excited Si(100) sample.

    View details for PubMedID 25273702

  • Atomic-Scale Perspective of Ultrafast Charge Transfer at a Dye-Semiconductor Interface JOURNAL OF PHYSICAL CHEMISTRY LETTERS Siefermann, K. R., Pemmaraju, C. D., Neppl, S., Shavorskiy, A., Cordones, A. A., Vura-Weis, J., Slaughter, D. S., Sturm, F. P., Weise, F., Bluhm, H., Strader, M. L., Cho, H., Lin, M., Bacellar, C., Khurmi, C., Guo, J., Coslovich, G., Robinson, J. S., Kaindl, R. A., Schoenlein, R. W., Belkacem, A., Neumark, D. M., Leone, S. R., Nordlund, D., Ogasawara, H., Krupin, O., Turner, J. J., Schlotter, W. F., Holmes, M. R., Messerschmidt, M., Minitti, M. P., Gul, S., Zhang, J. Z., Huse, N., Prendergast, D., Gessner, O. 2014; 5 (15): 2753-2759

    Abstract

    Understanding interfacial charge-transfer processes on the atomic level is crucial to support the rational design of energy-challenge relevant systems such as solar cells, batteries, and photocatalysts. A femtosecond time-resolved core-level photoelectron spectroscopy study is performed that probes the electronic structure of the interface between ruthenium-based N3 dye molecules and ZnO nanocrystals within the first picosecond after photoexcitation and from the unique perspective of the Ru reporter atom at the center of the dye. A transient chemical shift of the Ru 3d inner-shell photolines by (2.3 ± 0.2) eV to higher binding energies is observed 500 fs after photoexcitation of the dye. The experimental results are interpreted with the aid of ab initio calculations using constrained density functional theory. Strong indications for the formation of an interfacial charge-transfer state are presented, providing direct insight into a transient electronic configuration that may limit the efficiency of photoinduced free charge-carrier generation.

    View details for DOI 10.1021/jz501264x

    View details for Web of Science ID 000340222200044

    View details for PubMedID 26277975

  • Time-Resolved X-Ray Photoelectron Spectroscopy Techniques For Real-Time Studies Of Interfacial Charge Transfer Dynamics 22nd International Conference on the Application of Accelerators in Research and Industry (CAARI) Shavorskiy, A., Cordones, A., Vura-Weis, J., Siefermann, K., Slaughter, D., Sturm, F., Weise, F., Bluhm, H., Strader, M., Cho, H., Lin, M., Bacellar, C., Khurmi, C., Hertlein, M., Guo, J., Tyliszczak, T., Prendergast, D., Coslovich, G., Robinson, J., Kaindl, R. A., Schoenlein, R. W., Belkacem, A., Weber, T., Neumark, D. M., Leone, S. R., Nordlund, D., Ogasawara, H., Nilsson, A. R., Krupin, O., Turner, J. J., Schlotter, W. F., Holmes, M. R., Heimann, P. A., Messerschmidt, M., Minitti, M. P., Beye, M., Gul, S., Zhang, J. Z., Huse, N., Gessner, O. AMER INST PHYSICS. 2013: 475–479

    View details for DOI 10.1063/1.4802374

    View details for Web of Science ID 000319997900095

  • Discontinuity of the ultrafast electronic response of underdoped superconducting Bi2Sr2CaCu2O8+delta strongly excited by ultrashort light pulses PHYSICAL REVIEW B Giannetti, C., Coslovich, G., Cilento, F., Ferrini, G., Eisaki, H., Kaneko, N., Greven, M., Parmigiani, F. 2009; 79 (22)

    View details for DOI 10.1103/PhysRevB.79.224502

    View details for Web of Science ID 000267699300090

https://orcid.org/0000-0002-1601-1287