Reentrant Superconductivity in UTe 2
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Reentrant Superconductivity in UTe2 V. P. Mineev 1) Univ. Grenoble Alpes, Commissariat a l’Energie Atomique, PHELIQS, GT, F-38000 Grenoble, France Landau Institute for Theoretical Physics, 142432 Chernogolovka, Russia Submitted 3 May 2020 Resubmitted 12 May 2020 Accepted 12 May 2020
The reentrant superconductivity is the peculiar phenomenon observed in paramagnetic metal UTe2 in magnetic field parallel to the hard magnetisation axis. It is difficult to explain it in terms of field dependent intensity of magnetic fluctuations like it is done for explanation of the formally similar phenomena in the ferromagnetic uranium superconductors URhGe, UCoGe. Extremely large initial slope of the upper critical field temperature dependence suggests that the phenomenon has quasi-two-dimensional nature. Indeed, according to the recent band structure calculations by Y. Xu et al. (Phys. Rev. Lett. 123, 217002 (2019)) the Fermi surface of UTe2 consists of two types slightly corrugated cylinders. The theory of reentrant superconductivity in UTe2 based on its quasi-two-dimensional structure is presented here. DOI: 10.1134/S0021364020120036
I. Introduction. The superconductivity in the metallic compound UTe2 with orthorhombic structure has been discovered in December 2018 by Nicholas Butch and colleagues [1]. Almost immediately the discovery has been confirmed by the mixed FrenchJapanese team [2]. Since that time dozens studies of different properties of this material have been published. The most impressive observation [3, 4] was that the superconducting state UTe2 in the magnetic field aligned along the b-axis, which is perpendicular to the direction of easy magnetisation parallel to a-axis, persists up to 34.5 T where the superconductivity is destroyed by the metamagnetic transition. The magnetic field first reduces transition temperature to superconducting state, then in the field interval (10 T, 27 T) Tc (H) is almost field independent and finally near the metamagnetic transition the transition temperature increases practically recreating its zero field magnitude [5], see Fig. 1. Even more astonishing was that sweeping magnetic fields above the metamagnetic transition through the angular range 20◦ −40◦ from the b-axis towards the c-axis reveals a superconducting phase inside the dome, with the maximum value exceeding 65 T, the maximum field possible in the measurements (see Fig. 1a, c in [3]). The critical temperature of transition in superconducting state in this material is 1.5 K. The extremely high upper critical field at such modest critical temperature indicates that in this compound the paramagnetic depairing mechanism does not work and the 1) e-mail:
Fig. 1. (Color online) Sketch of the critical temperature Tc (H) magnetic field dependence in UTe2 for field parallel to b-axis according to the paper [5]. N, S, NF stand for normal, superconducting and normal ferromagnetic phases correspondingly. Thin straight dashed line shows abnormally large initial slope of Hc2 (T ) temperature dependence
superconducting state is formed by the electron pa
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