APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session F24: Probing Magnetic and Charge Degrees of Freedom in Spin-Triplet Superconductor UTe2
8:00 AM–11:00 AM,
Tuesday, March 7, 2023
Room: Room 237
Sponsoring
Unit:
DCMP
Chair: Johnpierre Paglione, University of Maryland, College Park
Abstract: F24.00005 : Probing penetration depth and residual loss anisotropy of high-Tc superconducting UTe2*
10:24 AM–11:00 AM
Abstract
Presenter:
Steven M Anlage
(University of Maryland, College Park)
Authors:
Steven M Anlage
(University of Maryland, College Park)
Arthur Carlton-Jones
(University of Maryland)
The recent discovery of unconventional superconductivity in UTe2 has motivated careful studies of the electrodynamic properties of single crystals of this material [PRB 100, 220504 (2019); Nat. Comms 12:2644 (2021); arXiv:2105.13721]. The magnetic penetration depth shows a power-law temperature dependence at low temperatures in the superconducting state. The microwave losses show a large residual value, and its origin may be due to surface states of potentially intrinsic character. We extend the electrodynamics measurements to a new generation of UTe2 crystals and extract the complex surface impedance Zs and complex conductivity σ=σ1-iσ2 as a function of temperature from 100 mK to 20 K, over 5-12 GHz. Recent studies [PRB 106, L060505, (2022)] indicate that the normal state and superconducting properties of UTe2 are anisotropic. We extend the cavity perturbation measurements to multiple resonant modes, each of which excites microwave currents in different crystallographic directions. This allows extraction of the anisotropic electrodynamic properties as a function of temperature, including the anisotropic magnitude of the screening length. We find that the penetration depth in new generation crystals (Tc=1.95 K) shows a robust power-law temperature dependence at low temperatures for currents in all directions, with exponents near 2, similar to the previous generation of UTe2 crystals. Substantial residual resistance is seen in all UTe2 crystals (old and new generation) and modes. This is expected for nodal superconductors, but it appears to be stronger than expected for point nodes alone. Our results are generally consistent with predictions of direction-independent power-law temperature dependence of the penetration depth in a generic topological superconductor having Weyl nodes and surface states [PRL 124, 067001 (2020)]. The results are also generally consistent with enhanced losses associated with the recently proposed topological anomalous skin effect [PRB 103, 104517 (2021)]. We will discuss the electrodynamic properties of the super- and normal-fluids in UTe2 in light of this new data, and other measurements, as well as ongoing efforts to understand this unique material.
*Electrodynamics work supported by NSF DMR2004386 (support of A.C.J.) and DOE grant No. DE-SC 0017931 (support of S.A.).