Weak antilocalization induced by Se substitution in layered BiCh$_2$-based (Ch = S, Se) superconductors LaO$_{1-x}$F$_x$BiS$_{2-y}$Se$_y$

TL;DR

This study investigates how selenium substitution affects the electronic transport and weak antilocalization phenomena in layered BiCh2-based superconductors, revealing tunable quantum interference effects linked to electronic ordering.

Contribution

It demonstrates the emergence and modulation of weak antilocalization in BiCh2 superconductors through Se substitution, highlighting the interplay with charge-density waves and superconductivity.

Findings

WAL observed in heavily Se-substituted samples.

Se substitution influences resistivity and Hall coefficient behaviors.

WAL-WL crossover linked to F and Se concentrations.

Abstract

We report transport properties for layered BiCh2-based (Ch = S, Se) superconductors LaO1-xFxBiS2-ySey (x = 0.2, 0.5, y = 0-1.05) and the observation of weak antilocalization (WAL). Electrical resistivity and Hall coefficients for the Se-poor samples increase with decreasing temperature. The increase becomes less pronounced with increasing Se concentration indicating a loss of insulating behavior. Interestingly, the moderately Se-substituted samples exhibit metallic behavior in the high-temperature region and a weak increase in the resistivity in the low-temperature regions, which indicates the existence of carrier localization. The heavily Se-substituted compounds show metallic behavior in the entire-temperature region. Sign changes of the Hall coefficients are observed for the x = 0.2 samples, which possibly is related to a charge-density wave (CDW). Magnetoresistance measurements indicate that WAL is realized in the heavily Se-substituted systems. The WAL behavior is weakened by the changes in F and Se concentrations. A crossover state of the WAL and WL emerges around the moderately F-doped and Se-free LaO0.8F0.2BiS2. The change of the resistivity behavior by the F and Se substitution clearly correlates to the difference of the magnetoconductance. Moreover, the localization regions of the WAL-WL crossover and weak WAL states are possibly associated with the CDW. We propose that the BiCh2-based system is a good platform for studying relationship between WAL, superconductivity, and electronic ordering because those states are tunable by element substitutions with bulk single crystals.