SKM 2021 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 19: Unconventional Superconductors

TT 19.4: Talk

Thursday, September 30, 2021, 12:00–12:15, H6

Twisted Superconductivity in the high magnetic field phase of CeRh₂As₂ — •Aline Ramires¹ and David Möckli² — ¹Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland — ²Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, Brazil

CeRh₂As₂, a locally noncentrosymmetric heavy fermion material, was recently reported to host a remarkable magnetic field versus temperature phase diagram with two superconducting phases and upper critical fields much above the Pauli limit [1]. In this material, the two inequivalent Ce sites per unit cell, related by inversion symmetry, introduce a sublattice structure corresponding to an extra internal degree of freedom. In this talk, I briefly review some mechanisms that allow for Pauli limit violation and discuss what properties of the normal state are key for the development of a superconducting state robust against magnetic fields. I discuss intra-sublattice and inter-sublattice pairing scenarios and how we can construct superconducting states that violate the Pauli limit by twisting the most stable superconducting state with respect to the internal sublattice degree of freedom [2]. I will also comment on ongoing work that highlights the role of normal state electronic structure parameters, as well as effects of impurities, and subleading instabilities in the phase diagram of this material [3].
[1] S. Khim et al., arXiv:2101.09522 (2021)
[2] D. Möckli and A. Ramires, Phys. Rev. Research 3, 023204 (2021)
[3] D. Möckli and A. Ramires, arXiv:2107.09723 (2021)