X-Ray Scattering Study of the Superconductor BKBO

Abstract

Microscopically, the properties of many superconductors can be explained by the Nobel Prize-winning Bardeen–Cooper–Schrieffer (BCS) theory. In this model, below a certain critical temperature Tc, electrons form pairs due to their interaction with atomic lattice vibrations and condense into a macroscopic quantum ground state. The potassium-doped bismuthate BKBO is notable for its relatively high Tc of just above 30 K (for x ~ 0.4). In this material, however, it still is not certain whether superconductivity is conventional with particularly strong electron-phonon coupling, or whether it involves a more exotic pairing mechanism. To better understand the pairing mechanism in BKBO, it is crucial to explore its complex electronic and structural properties. Therefore, we utilized the X-ray scattering instruments at the University of Minnesota’s Characterization Facility to study the structure of BKBO. We successfully identified the structural homogeneity and mosaicity of many samples, and Bragg peaks in sample diffraction patterns were consistent with calculations based on BKBO’s cubic structure. In the long-term, we aim to develop a deeper understanding of structural and electronic correlations, including the evolution from the charge density wave (CDW) order at x = 0 to the superconducting phase.