SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 28: Unconventional Superconductors

TT 28.2: Vortrag

Mittwoch, 29. März 2023, 09:45–10:00, HSZ 103

Superconductivity versus quadrupole density wave in CeRh₂As₂ — •Konstantin Semeniuk¹, Daniel Hafner¹, Pavlo Khanenko¹, Javier Landaeta¹, Thomas Lühmann¹, Christoph Geibel¹, Seunghyun Khim¹, Elena Hassinger², and Manuel Brando¹ — ¹MPI-CPfS, Dresden, Germany — ²TU Dresden, Dresden, Germany

A heavy-fermion superconductor CeRh₂As₂ (T_c≈0.3 K) undergoes a phase transition at the temperature T₀≈0.5 K, proposed to be a quadrupole density wave (QDW) instability. The compound hosts two distinct superconducting (SC) phases, presumably of different parity. These are separated by a first order phase boundary at magnetic field µ₀H^*=4 T, applied along the c axis of the tetragonal lattice. Recent studies suggest that the QDW phase boundary could meet the T_c(H) line at exactly at H^*. This would imply that the SC phase switching is driven by the field-induced suppression of the QDW order coexisting with the superconductivity. Inability to reliably track T₀ near 4 T has left the question standing.

We present a study of a new generation of CeRh₂As₂ crystals, showing sharper signatures of phase transitions. From our measurements of heat capacity and electrical resistivity in c-axis magnetic field, we produce a more detailed phase diagram which shows that the QDW and SC phase boundaries meet at 6 T. We conclude that the QDW state is not responsible for the SC phase switching at H^* and discuss the possible interplay between the two orders with reference to the Fermiology of CeRh₂As₂ as well as thermodynamic considerations.