Investigating the crystal field ground state and the limits of superconductivity in UTe<sub>2</sub>

ORAL

Abstract

Spin-triplet bulk superconductors are a promising route to topological superconductivity, and UTe2 is a recently discovered contender. The superconducting properties of UTe2, however, vary substantially as a function of the synthetic route, and even nonsuperconducting single crystals have been reported. To understand the driving mechanism suppressing superconductivity, we investigate UTe2 single crystals grown close to the nonsuperconducting boundary (growth temperature ~ 710 oC) through a combination of thermodynamic and x-ray diffraction measurements. Specific heat measurements reveal a sharp decrease in the superconducting volume and a concomitant increase in the residual specific heat coefficient near the nonsuperconducting boundary. Notably, these crystals are inhomogeneous and show an apparent double transition in specific heat measurements, similar to

samples grown at much higher temperatures (~ 1000 oC). Our single crystal x-ray diffraction measurements reveal that there are two important tuning

parameters: uranium vacancies and the atomic displacement along the c axis. We will discuss the relationship between these changes in superconducting properties and the crystalline electric field ground state of UTe2.

*This material is based upon work supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Science Center. Scanning electron microscope and energy dispersive x-ray measurements were performed at the Electron Microscopy Lab and supported by the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy Office of Science. AW and MMB acknowledge support from the Los Alamos Laboratory Directed Research and Development program.

–

Publication: A Weiland et al, J. Phys. Mater. 5 044001 (2022).
PFS Rosa et al, Communications Materials 3, 33 (2022).

Presenters

  • Priscila Rosa

    • Los Alamos National Laboratory

Authors

  • Priscila Rosa

    • Los Alamos National Laboratory

  • Ashley Weiland

    • Los Alamos National Laboratory

  • Mitchell Bordelon

    • Los Alamos National Laboraratory

  • Filip Ronning

    • Los Alamos Natl Lab

  • Joe D Thompson

    • Los Alamos National Laboratory
    • Los Alamos Natl Lab

  • Eric D Bauer

    • Los Alamos Natl Lab

  • Sean Thomas

    • Los Alamos National Laboratory