Events

Department of Magnetic Reseach Seminar

Locally non-centrosymmetric heavy-fermion superconductor CeRh2As2

dr Seunghyun Khim

Instytut Maxa Plancka Fizyki Chemicznej Ciał Stałych w Dreźnie w Niemczech

Seminarium odbędzie się zdalnie w aplikacji Microsoft Teams. W celu wzięcia udziału w wydarzeniu należy dołączyć do zespołu Seminarium OBM.Można do niego dołączyć na stałe przy użyciu kodu dostępu ol7omod (dotyczy to osób posiadających konto w domenie intibs.pl, pozostałe osoby proszę o kontakt z prof. dr. hab.Adamem Pikulem, prof. INTiBS PAN ())

Streszczenie:

The recently discovered CeRh2As2 has been attracting attention to the unusual two-phase superconductivity [1]. A clear thermodynamic phase transition within the superconducting (SC) state separates it into a low- and high-field phase. Strong Pauli-paramagnetic pair breaking in the low-field phase and an enhanced upper critical field (Hc2) of the high-field phase indicate a field-induced transition between an even- to odd-parity SC order parameter. CeRh2As2 has the centrosymmetric CaBe2Ge2-type structure which lacks local inversion symmetry at the Ce site. This gives rise to antisymmetric spin-orbit couplings that allow the two distinct SC phases to be very close in energy. As a result, an external field of 4 T switches a dominating SC order parameter from one to another to result in the unique Hc2 phase diagram.

The role of Ce-4f electron in CeRh2As2, however, seems not restricted to superconductivity. In this talk, I will summarize recent experimental progress that revealed intriguing normal state properties. As-NQR measurements observed a site-selective line broadening below TN ~ 0.27 K, suggesting an antiferromagnetic order in the superconducting state [2,3]. In-depth high-field measurements established a rich phase diagram of the unknown hidden order at T0 = 0.4 K, which is claimed to be the quadrupolar density wave order of the electronic Ce moments [4]. Muon spin relaxation/rotation measurements in various temperatures and magnetic fields characterized the normal state magnetic properties as well as the structure of the superconducting order parameter [5].

[1] S. Khim, J. Landaeta et al, Science 373, 1012 (2021).
[2] M. Kibune et al., Phys. Rev. Lett. 128, 057002 (2022).
[3] S. Kitagawa et al., J. Phys. Soc. Jpn. 91, 043702 (2022).
[4] D. Hafner et al., Phys. Rev. X 12, 011023 (2022).
[5] S. Khim et al., in preparation.