Intrinsic Phase Diagram of Superconductivity in the BiCh2-based System Without In-plane Disorder

TL;DR

This study reveals the intrinsic superconducting phase diagram of BiCh2-based layered compounds by showing that in-plane disorder is suppressed and superconductivity is induced by electron doping, with a flat Tc dependence.

Contribution

It provides the first detailed phase diagram of BiCh2-based superconductors considering the suppression of in-plane disorder, highlighting the intrinsic properties.

Findings

In-plane disorder is fully suppressed in LaO1-xFxBiSSe.

Superconductivity is induced at low doping levels (x=0.05, 0.1).

The Tc vs. doping phase diagram is notably flat.

Abstract

We have investigated the crystal structure and physical properties of LaO1-xFxBiSSe to reveal the intrinsic superconductivity phase diagram of the BiCh2-based layered compound family. From synchrotron X-ray diffraction and Rietveld refinements with anisotropic displacement parameters, we clearly found that the in-plane disorder in the BiSSe layer was fully suppressed for all x. In LaO1-xFxBiSSe, metallic conductivity and superconductivity are suddenly induced by electron doping even at x = 0.05 and 0.1 with a monoclinic structure. In addition, x (F concentration) dependence of the transition temperature (Tc) for x = 0.2-0.5 with a tetragonal structure shows an anomalously flat phase diagram. With these experimental facts, we have proposed the intrinsic phase diagram of the ideal BiCh2-based superconductors with less in-plane disorder.