Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 24: Unconventional Superconductors

TT 24.10: Talk

Wednesday, March 19, 2025, 12:30–12:45, H31

Symmetry-Preserving First-Order Superconductor-to-Superconductor Transition in Heavy-Fermion CeRh₂As₂ — •Fabian Jakubczyk^1,2, Julia Link^1,2, and Carsten Timm^1,2 — ¹TU Dresden, 01062 Dresden, Germany — ²Würzburg-Dresden Cluster of Excellence ct.qmat, TU Dresden, 01062 Dresden, Germany

Locally noncentrosymmetric materials are attracting significant attention due to the unique phenomena associated with sublattice degrees of freedom. The recently discovered heavy-fermion superconductor CeRh₂As₂ has emerged as a compelling example of this class, garnering widespread interest for its remarkable H-T phase diagram, which features field-induced multi-phase superconductivity with non-trivial angular dependencies and large critical fields, as well as antiferromagnetic order, and potential higher multipole orders. To investigate the complex interplay of the ordered phases in CeRh₂As₂ including the impact of a magnetic field, we develop a theoretical framework based on group-theoretical considerations, combined with Bogoliubov–de Gennes and Ginzburg–Landau methods. This approach enables us to propose probable symmetries of the superconducting states and elucidate their close relationship with magnetism in this material. Intriguingly, we find that the dominant first-order transition can be interpreted as a transition between coexistence phases of the same symmetry but with distinct admixtures of individual order parameters. Our approach accurately reproduces current experimental phase diagrams, both if the transition to a magnetic phase occurs below the superconducting critical temperature and if it occurs above.

Keywords: heavy-fermion; locally noncentrosymmetric materials; multiphase superconductivity; field-induced parity transition; CeRh2As2