摘要：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 BiCh 2 -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 Bi 4 O 4 S 3 . In this study, we investigated the isotope effects of 32 S and 34 S in the high-pressure phase of (Sr,La)FBiS 2 , 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)FBiS 2 are different from the unconventional isotope effects observed in La(O,F)BiSSe and Bi 4 O 4 S 3 , which have a tetragonal structure. The obtained results suggest that the pairing mechanisms of BiCh 2 -based superconductors could be switched by a structural-symmetry change in the superconducting layers induced by pressure effects.
