CeRh2As2 is a multi-phase superconductor with Tc=0.26K. The two superconducting (SC) phases, SC1 and SC2, observed for a magnetic field H parallel to the c axis of the tetragonal unit cell, have been interpreted as even- and odd-parity SC states, separated by a phase boundary at μ0H∗=4T. Such parity switching is possible due to a strong Rashba spin-orbit coupling at the Ce sites located in locally non-centrosymmetric environments of the globally centrosymmetric lattice. Existence of another ordered state (Phase I) below a temperature T0≈0.4K suggests an alternative interpretation of the H∗ transition: It separates a mixed SC+I (SC1) and a pure SC (SC2) state. Here, we present a detailed study of higher quality single crystals of CeRh2As2, showing much sharper signatures at Tc=0.31K and T0=0.48K. We refine the T-H phase diagram of CeRh2As2 and demonstrate that T0(H) and Tc(H) lines meet at μ0H≈6T, well above H∗, implying no influence of Phase I on the SC phase switching. A basic analysis with the Ginzburg-Landau theory indicates a weak competition between the two orders.
@article{arxiv.2301.09151,
title = {Decoupling multi-phase superconductivity from normal state ordering in CeRh$_2$As$_2$},
author = {Konstantin Semeniuk and Daniel Hafner and Pavlo Khanenko and Thomas Lühmann and Jacintha Banda and Javier F. Landaeta and Christoph Geibel and Seunghyun Khim and Elena Hassinger and Manuel Brando},
journal= {arXiv preprint arXiv:2301.09151},
year = {2024}
}