Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 38: f-Electron Systems and Heavy Fermions

TT 38.1: Hauptvortrag

Mittwoch, 3. April 2019, 09:30–10:00, H23

A new heavy-fermion superconductor CeRh₂As₂ with Rashba and quadrupolar interactions — •Seunghyun Khim, Jacintha Banda, Daniel Hafner, Ulrike Stockert, Manuel Brando, and Christoph Geibel — Max Planck Institut für Chemische Physik fester Stoffe, Dresden, Germany

One of the hot topic in the field of superconductivity is the effect of breaking inversion symmetry in the presence of strong spin-orbit interactions. This leads to a spin-splitted Fermi surface with unique momentum-locked spin polarization. Superconductivity appearing from such polarized bands is robust against Zeeman pair-breaking effect and can host mixed-parity pairing providing exotic superconducting states. Here, we report the discovery of heavy-fermion superconductivity in CeRh₂As₂ with T_c ∼ 0.25 K. This compound crystallizes in the CaBe₂Ge₂-type structure where inversion symmetry is locally broken at the Ce site. We observe a huge upper critical field of 12 T for the out-of-plane direction surpassing the Pauli-paramagnetic limit of ∼ 0.5 T. This provides a clear signature of a Rashba-type in-plane spin polarization arising from an alternating asymmetric potential due to the broken local inversion symmetry. In addition, our results indicate this system to be very close to a quantum critical point (QCP) with a further transition at T_o ∼ 0.4 K, likely of quadrupolar nature. Therefore, CeRh₂As₂ is a promising candidate for studying how heavy-fermion superconductivity behaves under the influence of Rashba-type interactions and a possible multipolar QCP.