Local inversion-symmetry breaking in a crystal combined with strong Rashba interaction can lead to a field-induced transition from an even to an odd-parity superconducting state, when the orbital limit is large due to correlations [1]. The first realisation of this phenomenology is likely found in the locally non-centrosymmetric CeRh2As2 in which two superconducting states (SC1 and SC2) occur in a magnetic field along the crystallographic c axis [2,3]. The superconducting state with Tc = 0.3 K develops out of an ordered state setting in at T0 = 0.5 K [4] of possibly quadrupole-density-wave (QDW) origin. Furthermore, signatures of antiferromagnetism (AF) are observed below Tc by NQR [5]. The low ordering temperatures and non-Fermi-liquid behavior suggest the proximity to a quantum critical point but the role of QDW and AF orders for superconductivity remains unclear. In this talk I will give a comprehensive overview of experimental results on this unique material including the discovery [2], the strong anisotropy of the phase diagram for different field directions [2,4,6] along with the detailed angle dependence [3], as well as the response to hydrostatic pressure. These results support the even to odd-parity transition scenario for the superconducting states and suggest a weak competitive coupling between the QDW and SC order parameters [6].

[1] T. Yoshida et al., Phys. Rev. B 86, 134514 (2012).

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

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

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

[5] K. Kibune et al., Phys. Rev. Lett. 128, 057002 (2022).

[6] K. Semeniuk et al., arXiv:2301.09151 (2023).

Contact : florence.levy-bertrand@neel.cnrs.fr