Berlin 2024 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 67: Unconventional Superconductors

TT 67.6: Talk

Thursday, March 21, 2024, 11:00–11:15, H 3007

Field-induced compensation of magnetic exchange as the possible origin of reentrant superconductivity in UTe₂ — •Toni Helm¹, Motoi Kimata², Kenta Sudo², Atsuhiko Miyata¹, Markus Koenig³, Ilya Sheikin⁴, Alexandre Pourret⁵, Georg Knebel⁵, Dai Aoki², Jochen Wosnitza¹, and Jean-Pascal Brison⁵ — ¹Dresden High Magnetic Field Laboratory, Helmholtz-Zentrum Dresden-Rossendorf, Germany — ²IMR, Tohoku University, Japan — ³Max Planck Institute CPfS Dresden, Germany — ⁴LNCMI Grenoble, France — ⁵CEA, University des Alpes, Grenoble, France

The potential spin-triplet heavy-fermion superconductor UTe₂ exhibits signatures of multiple distinct superconducting phases. For field aligned along the b axis, a metamagnetic transition occurs at µ₀H_m= 35 T. It is associated with magnetic fluctuations that may be beneficial for the field-reinforced superconductivity surviving up to H_m. Once the field is tilted away from the b towards the c axis, a reentrant superconducting phase emerges just above H_m. We conducted magnetic-torque and magnetotransport measurements in pulsed magnetic fields. We determine the record-breaking upper critical field of µ₀H_c2≈ 73 T and its evolution with angle. Furthermore, the normal-state Hall effect experiences a drastic suppression indicative of a reduced band polarization above H_m in the angular range around 30^∘ caused by a partial compensation between the applied field and an exchange field. This promotes the Jaccarino-Peter effect as a likely mechanism for the reentrant superconductivity above H_m.

Keywords: Heavy Fermion Superconductors; High Magnetic Fields; Magnetotransport; Reentrant Superconductivity