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TT: Fachverband Tiefe Temperaturen

TT 29: Unconventional Superconductors

TT 29.6: Vortrag

Dienstag, 10. März 2026, 10:45–11:00, CHE/0091

Entropy-rich superconductivity and unconventional vortex dynamics in CeRh₂As₂ — •Shuai Zhang, Xinyang Liu, Enke Liu, and Peijie Sun — Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China

We investigate the multiple superconducting (SC) phases SC1 and SC2 of CeRh₂As₂ using high-resolution magnetocaloric-effect (MCE) measurements. Pronounced temperature hysteresis observed during quasiadiabatic field sweeps provides direct thermodynamic evidence that both the SC1-normal (NS) and SC2-NS transitions are first order. In contrast, a continuous yet asymmetric entropy evolution across the SC1-SC2 boundary reveals a change in the superconducting order parameter, consistent with a second-order transition. The observed temperature dips in field-sweep traces identify SC2 as a higher-entropy phase compared with SC1 and NS. Furthermore, the two-step resistive transitions and enhanced Δ T near the SC2-NS boundary highlight the unconventional and current-sensitive nature of SC2. These results establish a comprehensive thermodynamic phase diagram for CeRh₂As₂ and demonstrate that MCE is a powerful probe of entropy discontinuities and symmetry reconstruction in locally noncentrosymmetric superconductors.

Keywords: CeRh2As2; magnetocaloric-effect; entropy evolution; thermodynamic; phase diagram