Evidence of Lattice Strain as a Precursor to Superconductivity in BaPb$_{0.75}$Bi$_{0.25}$O$_3$

TL;DR

This study investigates how lattice strain influences the emergence of superconductivity in BaPb$_{0.75}$Bi$_{0.25}$O$_3$, revealing precursor strain effects and electronic structure changes that lead to superconductivity around 11 K.

Contribution

It demonstrates that increased lattice strain above the critical temperature acts as a precursor to superconductivity in BaPb$_{0.75}$Bi$_{0.25}$O$_3$, combining experimental and theoretical insights.

Findings

Lattice strain increases between 10 K and 25 K, above $T_C$.

The compound shows a pseudogap formation with decreasing temperature.

Band structure calculations indicate gap closing due to Pb doping.

Abstract

In this work, we have investigated the precursor effects to superconductivity in BaPb$_{0.75}$Bi$_{0.25}$O$_3$ using temperature dependent resistivity, x-ray diffraction technique and photoemission spectroscopy. The present compound exhibits superconductivity around 11 K ($T_C$). The synthesis procedure adopted is much simpler as compared to the procedure available in the literature. In the temperature range (10 K-25 K) i.e. above $T_C$, our results show an increase in both the orthorhombic and tetragonal strain. The well screened features observed in Bi and Pb 4$f_{7/2}$ core levels are indicative of the metallic nature of the sample. The compound exhibits finite intensity at the Fermi level at 300 K and this intensity decreases with decrease in temperature and develops into a pseudogap; the energy dependence of the spectral density of states suggests disordered metallic state. Furthermore, our band structure calculations reveal that the structural transition upon Pb doping results in the closing of the band gap at the Fermi level.