Konstantin Semeniuk I Superconductivity and quadrupole density wave in CeRh2As2

Konstantin Semeniuk, Max Planck Institute for Chemical Physics of Solids, Dresden, Germany

The Kondo lattice compound CeRh₂As₂ is an unconventional superconductor (T_c ≈ 0.3 K) exhibiting a first order transition between two distinct superconducting states when magnetic field is applied along the c axis of the tetragonal unit cell [1]. The high-field state is characterised by the odd-parity pairing and a purely orbital-limited upper critical field of at least 15 T [2]. One of the key ingredients for realising such a phase diagram is a strong Rashba spin-orbit coupling caused by the lack of local inversion symmetry at the Ce sites. Besides the superconductivity, CeRh₂As₂ also displays a phase transition at ~0.4 K, proposed to be a quadrupole-density-wave (QDW) instability [3].

In our latest experiments we investigated the interplay between the QDW state and superconductivity. Heat capacity and resistivity measurements on new higher-quality single crystals of CeRh₂As₂ clearly indicate that the QDW is not involved in the superconducting phase switching. This result is further reinforced by our high-pressure resistivity study, which at the same time strongly suggests the influence of the QDW order on the ab-plane upper critical field. We discuss potential scenarios of the interaction between the two states and consider their relevance in the context of quantum critical behaviour.

[1] S. Khim & J. Landaeta et al., Science 373, 1012–1016 (2021).

[2] J. Landaeta et al., Phys. Rev. X 12, 031001 (2022).

[3] D. Hafner et al., Phys. Rev. X 12, 011023 (2022).