Local inversion-symmetry breaking in a bismuthate high-$T_c$ superconductor

Abstract

The doped perovskite BaBiO${}_3$ exhibits a maximum superconducting transition temperature ($T_c$) of 34 K and was the first high-$T_c$ oxide to be discovered, yet pivotal questions regarding the nature of both the metallic and superconducting states remain unresolved. Although it is generally thought that superconductivity in the bismuthates is of the conventional s-wave type, the pairing mechanism is still debated, with strong electron-phonon coupling and bismuth valence or bond disproportionation possibly playing a role. Here we use diffuse x-ray scattering and Monte Carlo modeling to study the local structure of Ba${}_{1-x}$K${}_x$BiO${}_3$ across its insulator-metal boundary. We find no evidence for either long- or short-range disproportionation, which resolves a major conundrum, as disproportionation and the related polaronic effects are likely not relevant for the metallic and superconducting states. Instead, we uncover nanoscale structural correlations that break inversion symmetry, which has far-reaching implications for the electronic physics, including the pairing mechanism. This unexpected finding furthermore establishes that the bismuthates belong to the broader classes of materials with hidden spin-orbit coupling and a tendency towards inversion-breaking displacements.

arXiv comment23 pages, 3 main figures, extended data figures included

References in corpus (16)

• Superconductivity and spin-orbit coupling in non-centrosymmetric materials: a review
• Scalable T^2 resistivity in a small single-component Fermi surface
• Superconductivity in dilute SrTiO${}_3$: a review
• Uncovering and tailoring hidden Rashba spin-orbit splitting in centrosymmetric crystals
• High pressure floating-zone growth of perovskite nickelate LaNiO3 single crystals
• Discovery of Superconductivity in (Ba,K)SbO${}_3$
• Unveiling the superconducting mechanism of Ba${}_{0.51}$K${}_{0.49}$BiO${}_3$
• Momentum-Resolved Electronic Structure of the High-$T_c$ Superconductor Parent Compound BaBiO${}_3$
• Stripe-like nanoscale structural phase separation and optimal inhomogeneity in superconducting BaPb${}_{1-x}$Bi${}_x$O${}_3$
• Electron-Phonon Coupling and Electron-Phonon Scattering in SrVO${}_3$
• Ultrafast Calculation of Diffuse Scattering from Atomistic Models
• Quantum Monte Carlo study of lattice polarons in the two-dimensional multi-orbital Su-Schrieffer-Heeger model
• Theory of superconductivity mediated by Rashba coupling in incipient ferroelectrics
• Uniaxial strain control of bulk ferromagnetism in rare-earth titanates
• Polaron and bipolaron tendencies in a semiclassical model for hole-doped bismuthates
• Topological (Sliced) Doping of a 3D Peierls System: Predicted Structure of Doped BaBiO3

Cited by in corpus (4)

• Diffuse Scattering from Correlated Electron Systems
• Nanoscale structural correlations in a model cuprate superconductor
• Interleaved bond frustration in a triangular lattice antiferromagnet
• Persistence of small polarons into the superconducting phase of Ba${}_{1-x}$K${}_x$BiO${}_3$