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Structural and uranium valence change in UTe<sub>2</sub> and UFe<sub>2</sub>Si<sub>2</sub> detected by high pressure x-ray diffraction and resonant x-ray emission spectroscopy

ORAL

Abstract

High pressure x-ray diffraction studies in UTe2 up to 30 GPa at room temperature revealed an orthorhombic to tetragonal phase transition between 5 and 7 GPa [1,2,3], with a large volume collapse of nearly 10% and a nearest U-U distance increase by about 4% [1]. In conjunction, resonant x-ray emission spectroscopy and partial fluorescence yield x-ray absorption spectra clearly demonstrate a U intermediate valence of nearly +3.74 at 1.8 GPa and room temperature. With increasing pressure, the U valence shifts towards 4+, passes through a peak at 2.8 GPa, and then decreases towards 3+ and settles to nearly a constant value above 15 GPa and up to 52 GPa [1]. This lower to higher symmetry transition suggests less 5f electron participation in bonding when the weakly correlated superconducting phase in the tetragonal structure of UTe2 appears. Additionally, high pressure x-ray diffraction spectra in UFe2Si2 exhibit new peaks at P > 20 GPa – signaling a possible phase transition. UFe2Si2 resonant x-ray emission spectra are consistent with a valence of 3.7 at 1.5 GPa which steadily decreases to 3.6 up to 7 GPa, while data collected at 32 and 54 GPa indicates an increase in valence back to 3.7.

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Publication: [1] Yuhang Deng, Eric Lee-Wong, Camilla M. Moir , Ravhi S. Kumar , Nathan Swedan , Changyong Park , Dmitry Yu Popov , Yuming Xiao , Paul Chow , Ryan E. Baumbach, Russell J. Hemley , M. Brian Maple. Structural transition and uranium valence change in UTe2 at high pressure revealed by x-ray diffraction and spectroscopy. Physics Review B, 110, 075140 (2024)<br>[2] Fuminori Honda, Shintaro Kobayashi, Naomi Kawamura, Saori Kawaguchi, Takatsugu Koizumi, Yoshiki J. Sato, Yoshiya Homma, Naoki Ishimatsu, Jun Gouchi, Yoshiya Uwatoko, Hisatomo Harima, Jacques Flouquet, and Dai Aoki, "Pressure-induced structural transition and new superconducting phase in UTe2," J. Phys. Soc. Jpn. 92, 044702 (2023).<br>[3] Larissa Q. Huston, Dmitry Y. Popov, Ashley Weiland, Mitchell M. Bordelon, Priscila F. S. Rosa, Richard L. Rowland, II, Brian L. Scott, Guoyin Shen, Changyong Park, Eric K. Moss, S. M. Thomas, J. D. Thompson, Blake T. Sturtevant, and Eric D. Bauer, "Metastable phase of UTe2 formed under high pressure above 5 GPa," Phys. Rev. Mat. 6, 114801 (2022).

Presenters

  • Eric Lee-Wong

    University of California, San Diego, Department of Physics, University of California, San Diego, CA 92093, USA

Authors

  • Eric Lee-Wong

    University of California, San Diego, Department of Physics, University of California, San Diego, CA 92093, USA

  • Yuhang Deng

    University of California, San Diego, Department of Physics, University of California, San Diego, CA 92093, USA

  • Camilla M Moir

    University of California, San Diego, Department of Physics, University of California, San Diego, CA 92093, USA

  • Ravhi S Kumar

    Department of Physics, University of Illinois Chicago, Chicago, IL 60607, USA, University of Illinois at Chicago, Department of Physics, University of Illinois Chicago

  • Nathan Swedan

    Department of Physics, University of California, San Diego, CA 92093, USA

  • Changyong Park

    HPCAT, X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA, HPCAT, X-ray Science Division, Argonne National Laboratory

  • Dmitry Popov

    High Pressure Collaborative Access Team, X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA

  • Yuming Xiao

    High Pressure Collaborative Access Team, X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA

  • Paul Chow

    High Pressure Collaborative Access Team, X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA

  • Ryan E Baumbach

    Department of Physics, University of California, Santa Cruz, CA 95064, USA, UC Santa Cruz

  • Russell J Hemley

    University of Illinois at Chicago, University of Illinois Chicago, Departments of Physics, Chemistry, and Earth and Environmental Sciences, University of Illinois Chicago, Chicago, IL 60607, USA, Departments of Physics, Chemistry, and Earth and Environmental Sciences, University of Illinois Chicago

  • Peter S Riseborough

    Department of Physics, Temple University, Philadelphia, PA 19122, USA, Temple University

  • M. Brian Maple

    University of California, San Diego, University of California San Diego, Department of Physics, University of California, San Diego, CA 92093, USA