Superconductivity in La1-xCexOBiSSe: carrier doping by mixed valence of Ce ions

TL;DR

This study demonstrates that Ce ion mixed valence effectively induces electron doping, leading to superconductivity in La1-xCexOBiSSe, with a maximum Tc of 3.1 K, offering an alternative doping method for layered bismuth-chalcogenides.

Contribution

It introduces mixed valence Ce doping as a new approach to induce superconductivity in La1-xCexOBiSSe, expanding doping strategies for layered bismuth-chalcogenide superconductors.

Findings

Superconductivity observed for x=0.2-0.6 with Tc up to 3.1 K

Metallic behavior for x > 0.1 due to electron doping

Dome-shaped phase diagram of Tc versus doping level

Abstract

We report the effects of Ce substitution on structural, electronic, and magnetic properties of layered bismuth-chalcogenide La1-xCexOBiSSe (x = 0-0.9), which are newly obtained in this study. Metallic conductivity was observed for x > 0.1 because of electron carriers induced by mixed valence of Ce ions, as revealed by bond valence sum calculation and magnetization measurements. Zero resistivity and clear diamagnetic susceptibility were obtained for x = 0.2-0.6, indicating the emergence of bulk superconductivity in these compounds. Dome-shaped superconductivity phase diagram with the highest transition temperature (Tc) of 3.1 K, which is slightly lower than that of F-doped LaOBiSSe (Tc = 3.7 K), was established. The present study clearly shows that the mixed valence of Ce ions can be utilized as an alternative approach for electron-doping in layered bismuth-chalcogenides to induce superconductivity.