In-plane chemical pressure essential for superconductivity in BiCh2-based (Ch: S, Se) layered structure

TL;DR

This study reveals that in-plane chemical pressure is crucial for inducing and determining the superconducting transition temperature in BiCh2-based layered superconductors, providing insights into their structural mechanisms.

Contribution

It demonstrates that in-plane chemical pressure universally influences superconductivity and transition temperature in BiCh2-based superconductors, based on detailed crystal structure analysis.

Findings

In-plane chemical pressure enhances bulk superconductivity.

Superconducting transition temperature correlates with in-plane chemical pressure.

Crystal structure analysis links chemical pressure to superconducting properties.

Abstract

BiCh2-based superconductors (Ch: S, Se) are a new series of layered superconductor. However, mechanisms for the emergence of superconductivity in BiCh2-based superconductors have not been clarified. In this study, we have investigated crystal structure of two series of optimally-doped BiCh2-based superconductors, Ce1-xNdxO0.5F0.5BiS2 and LaO0.5F0.5Bi(S1-ySey)2, using powder synchrotron x-ray diffraction in order to reveal the relationship between crystal structure and superconducting properties of the BiCh2-based family. We have found that an enhancement of in-plane chemical pressure would commonly induce bulk superconductivity in both systems. Furthermore, we have revealed that superconducting transition temperature for REO0.5F0.5BiCh2 superconductors could universally be determined by degree of in-plane chemical pressure.