Decisive role of hybridized electronic states on the appearance of superconductivity in Ba1−xKxMO3 (M=Bi,Sb)

Abstract

The observation of superconductivity (SC) in hole-doped antimonates Ba1−xKxSbO3 (BKSO), isoelectronic compounds to bismuthate Ba1−xKxBiO3 (BKBO) SCs, enables a pathway to clarify the role of hybridizations between electronic states of metals and ligands on the emergence of SC. Herein, using first-principles simulations, the localized electronic structure of antimonates is demonstrated to produce various charge and bond orderings (CBOs) up to x=0.6, hence hindering the appearance of a SC state. This is in contrast with bismuthates where the formation of charge orderings is suppressed by doping effects and their native hybridized electronic structure. Although quenched by doping effects, the CBOs mediate the Cooper pair formation, and the resulting electron-phonon coupling reproduces the experimental facts such as a larger Tc in BKSO than in BKBO for x>0.65 and a maximal Tc of ∼30K observed at x=0.4−0.5 for BKBO. The latter point is ascribed to a soft phonon mode at x=0.5, while the former observation is ascribed to an intrinsically stronger coupling between lattice distortions and electrons in BaSbO3. Although materials with a localized electronic structure could warrant larger T′cs, the main drawback is the resilience of such compounds to form a metallic state, and hence SC emerges far away of soft phonons possessing a strong coupling with the electronic structure.

Source-reported materials — not catalogue approval

Similar papers