Superconducting-insulating quantum phase transition associated with valence change in compressed perovskite bismuth-oxides

Abstract

Searching for a universal trend by the same tuning method in different high-temperature superconductors with a similar crystal structure is a common strategy to find clues for a better understanding the superconducting mechanism in a unified way. It is known that the hole-doped bismuth-oxide Ba1-xKxBiO3 possesses a similar perovskite structure to that of the hole-doped copper-oxide (cuprate) superconductors but also holds a comparatively high superconducting transition temperature. In this study, we report the first observation of the pressure-induced quantum phase transition (QPT) from superconducting to insulating states in a series of Ba1-xKxBiO3 single-crystal samples. A similar QPT has also been observed recently in the compressed cuprate superconductors1. Significantly, we found that the QPT observed in Ba1-xKxBiO3 is intriguingly associated with the valence change of the Bi ions in the material. These results lead us to propose that the pressure-induced valence change from Bi3+ to Bi5+ destroys the hole-doping effect on stabilizing the conductivity and corresponding superconductivity. By comparing the high-pressure behaviors observed in these two kinds of oxides, we identified another prominent feature shared by them - the more the hole-doping concentration, the higher the critical pressure required for driving the QPT.

Synthesis and Characterization of High-Energy Anti-Perovskite Compounds Cs3X[B12H12] Based on Cesium Dodecahydro-Closo-Borate with Molecular Oxoanions (X− = [NO3]−, [ClO3]− and [ClO4]−)

“…Table 3. Molar volumes (V m in cm 3 •mol −1 ) of compounds (I) to (III), their precursor materials, and similar hydro-borate perovskites, with a comparison of the calculated sum of the components and the real values. V m (B) represents V m (Cs 2 [B 12 H 12 ]), and V m (C) represents V m (CsX) or V m (ice-I), respectively.…”

“…The perovskite crystal structure, with its distinctive ABX 3 composition, has long been a focal point in materials science [1] owing to its diverse range of applications, spanning from photovoltaics [2] to superconductors [3]. In recent years, a counterintuitive class of materials, referred to as anti-perovskites, has emerged as a promising avenue for scientific exploration [4].…”

“…With a mass calorific value of up to 58.7 MJ/kg [9,10], boron surpasses another typical metal fuel, such as aluminum (Al), by almost two times, since aluminum has a calorific value of 30.8 MJ/kg. Moreover, the volumetric calorific value of boron reaches an impressive 135.2 kJ/cm 3 , significantly exceeding that of Al (83.3 kJ/cm 3 ) by 51.9 kJ/cm 3 [11,12]. Boron-based, fuel-rich propellants typically comprise the non-metal fuel boron, oxidants, binders, and additives.…”