Materials with multiple superconducting phases are rare. Here, we report the discovery of two-phase unconventional superconductivity in CeRh₂As₂. Using thermodynamic probes, we establish that the superconducting critical field of its high-field phase is as high as 14 tesla, even though the transition temperature is only 0.26 kelvin. Furthermore, a transition between two different superconducting phases is observed in a c axis magnetic field. Local inversion-symmetry breaking at the cerium sites enables Rashba spin-orbit coupling alternating between the cerium sublayers. The staggered Rashba coupling introduces a layer degree of freedom to which the field-induced transition and high critical field seen in experiment are likely related.

具有多个超导相的材料很少见。在这里，我们报告了 CeRh ₂ As ₂中两相非常规超导性的发现。使用热力学探针，我们确定其高场相的超导临界场高达 14 特斯拉，即使转变温度仅为 0.26 开尔文。此外，在c轴磁场中观察到两个不同超导相之间的转变。铈位点的局部反转对称性破坏使 Rashba 自旋轨道耦合在铈亚层之间交替。交错的 Rashba 耦合引入了一个层自由度，实验中看到的场诱导转变和高临界场可能与此相关。