Dresden 2020 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 41: Unconventional Superconductors

TT 41.11: Vortrag

Mittwoch, 18. März 2020, 18:00–18:15, HSZ 201

Field-induced change of the superconducting state in the locally non-centrosymmetric heavy fermion CeRh2As2 — •Javier Landaeta, Seunghyun Khim, Daniel Hafner, Jacinta Banda, Manuel Brando, Robert Küchler, Christoph Geibel, and Elena Hassinger — Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany

CeRh2As2 is a new heavy fermion superconductor with a CaBe2Ge2-type crystalline structure, which lacks inversion symmetry locally at the Ce site. A weak phase transition is observed in the specific heat at T0=0.4 K with possibly quadrupolar origin and below Tc= 0.27 K the material becomes superconducting. Here, we present a comprehensive study of the low temperature AC magnetic susceptibility in a single crystal of CeRh2As2 up to 15 T. We did not detect any additional transition above Tc, supporting that the specific heat anomaly might be caused by a quadrupolar order. The superconducting upper critical field is strongly anisotropic with µ0Hc2= 13 T for Bc and µ0Hc2= 2 T for Bc, which exceed the Pauli limit. The large Hc2 and their anisotropy are reminiscent of non-centrosymmetric superconductors such as CePt3Si, CeRhSi3, CeIrSi3. What makes CeRh2As2 stand out is its unique superconducting phase diagram with a pronounced kink at 4 T for Bc reproducible in heat capacity, resistivity and AC susceptibility measurements. Moreover, isothermal AC susceptibility and magnetostriction reveal a sharp phase transition inside the superconducting phase at 4 T independent of temperature. Therefore, two different superconducting states exist for Bc in CeRh2As2.

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