Tunable electronic anisotropy in single-crystal A2Cr3As3 (A = K, Rb) quasi-one-dimensional superconductors

TL;DR

This study reports the growth and analysis of single-crystal A2Cr3As3 superconductors, revealing tunable electronic anisotropy linked to inter-chain spacing and demonstrating quasi-one-dimensional electronic behavior.

Contribution

It introduces a method for growing high-quality single crystals and uncovers how alkali metal size influences electronic anisotropy and transport properties in A2Cr3As3 superconductors.

Findings

Superconducting transition temperatures of 6.1 K and 4.8 K for K and Rb compounds.

Strong normal state electronic anisotropy observed in Rb2Cr3As3.

Enhanced conductivity and magnetoresistance linked to increased inter-chain spacing.

Abstract

Single crystals of A2Cr3As3 (A = K, Rb) were successfully grown using a self-flux method and studied via structural, transport and thermodynamic measurement techniques. The superconducting state properties between the two species are similar, with critical temperatures of 6.1 K and 4.8 K in K2Cr3As3 and Rb2Cr3As3, respectively. However, the emergence of a strong normal state electronic anisotropy in Rb2Cr3As3 suggests a unique electronic tuning parameter is coupled to the inter-chain spacing in the A2Cr3As3 structure, which increases with alkali metal ionic size while the one-dimensional [(Cr3As3)^{2-}]_{\infty} chain structure itself remains essentially unchanged. Together with dramatic enhancements in both conductivity and magnetoresistance (MR), the appearance of a strong anisotropy in the MR of Rb2Cr3As3 is consistent with the proposed quasi-one-dimensional character of band structure and its evolution with alkali metal species in this new family of superconductors.