Possible pairing mechanism switching driven by structural symmetry breaking in BiS₂-based layered superconductors.

ABSTRACT: Investigation of isotope effects on superconducting transition temperature (T_c) is one of the useful methods to examine whether electron-phonon interaction is essential for pairing mechanisms. The layered BiCh₂-based (Ch: S, Se) superconductor family is a candidate for unconventional superconductors, because unconventional isotope effects have previously been observed in La(O,F)BiSSe and Bi₄O₄S₃. In this study, we investigated the isotope effects of ³²S and ³⁴S in the high-pressure phase of (Sr,La)FBiS₂, which has a monoclinic crystal structure and a higher T_c of ~?10 K under high pressures, and observed conventional-type isotope shifts in T_c. The conventional-type isotope effects in the monoclinic phase of (Sr,La)FBiS₂ are different from the unconventional isotope effects observed in La(O,F)BiSSe and Bi₄O₄S₃, which have a tetragonal structure. The obtained results suggest that the pairing mechanisms of BiCh₂-based superconductors could be switched by a structural-symmetry change in the superconducting layers induced by pressure effects.

SUBMITTER: Yamashita A 

PROVIDER: S-EPMC7815720 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature