Quantum Matter Seminar 24th February: "High-field superconductivity in UTe2"

22 February 2023

This seminar is about the heavy-Fermion superconductor UTe2. It will be presented by Toni Helm (HLD-EMFL and Helmholtz Zentrum, Dresden).

Join the Quantum Matter group in a seminar titled "High-field superconductivity in UTe2" with Dr. Toni Helm (HLD-EMFL and Helmholtz Zentrum, Dresden).

Date: 24 February 2023, 3:00PM - 4:00PM

Location: Grid Access Room 3.29

Zoom link: https://bristol-ac-uk.zoom.us/j/94980851213?pwd=WWJWSXBwTHBweGd0cG1JQmlaZ29KZz09

Meeting ID: 949 8085 1213

Passcode: 257531

Abstract:

The heavy-Fermion superconductor UTe2 is a potential candidate for a spin-triplet superconducting ground state that emerges below 2 K [1,2]. The material is a highly anisotropic paramagnet that exhibits a metamagnetic transition at HM = 35 T for field aligned along the b axis [3]. This transition is associated with a spin reorientation, inducing magnetic fluctuations that may be beneficial for the field-enhanced superconductivity surviving up to HM. Once the field is tilted away from the b towards the c axis, a reentrant superconducting phase emerges just above HM(θ). In addition, field- and pressure-induced superconducting phases with signatures of distinct order parameters have been revealed, adding to the complexity of this material [4,5]. These are only a few of the most recent exciting findings for UTe2, leaving many open questions, e.g., about the role of magnetism in the establishment of its unconventional superconducting ground state. In order to better understand the remarkably field-resistant superconductivity we investigated magnetotransport and magnetic torque in pulsed magnetic field up to 70 T for FIB-microfabricated devices. Our findings confirm the existence of the high-field reentrant superconducting phase for a tilt angle around θ = 30° off the b axis above 40 T. We determined the upper critical field to Hc2  75 T. Furthermore, the anomalous Hall effect in the normal-state exhibits a drastic suppression in the vicinity of the high-field superconductivity. This new finding calls to revisit the interpretation of the anomalous Hall effect in UTe2, and allows a first suggestion of a mechanism for the high-field superconducting phase.

Further information

[1] S. Ran et al., Science 365, 684 (2019).

[2] D. Aoki et al., J. Phys. Soc. Jpn. 88, 043702 (2019).

[3] Q. Niu et al., Phys. Rev. Res 2, 033179 (2020).

[4] D. Aoki et al., J. Phys. Soc. Jpn. 90, 074705 (2021).

[5] S. Ran et al., Nat. Phys.15, 1250-1254 (2019)

[6] T. Helm et al., arXiv.2207.08261 (2023)