Condensed Matter Journal Club: "Optical signature of the excited Cooper pair collective mode in the locally non-centrosymmetric superconductor CeRh2As2"

Abstract: On the experimental observation of a field-induced first order transition in the superconducting state of CeRh2As2, which is a possible indication of a parity-switching transition of the superconductor, the microscopic physics is still under investigation. However, if two competing pairing channels of opposite parities do exist, a particle-particle collective mode referred to as the Bardasis-Schrieffer (BarSch) mode may be present below the pair-breaking continuum. The BarSch mode of the CeRh2As2 superconductor can couple to the light, as it arises from a pairing channel with the parity opposite to that of the superconducting condensate. Here, by using a generic model Hamiltonian, we carry out a qualitative investigation on the excitation energy of the BarSch mode with respect to the out-of-plane magnetic fields and its contribution to the optical conductivity [1]. Our findings indicate that the distinct coupling between the BarSch mode and the light can serve as evidence for the competing odd-parity channels of CeRh2As2 and other locally non-centrosymmetric superconductors.

Ref [1] Changhee Lee and Suk Bum Chung, Commun. Phys. 6, 972 (2023).