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

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 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 interchain spacing in the A2Cr3As3 structure, which increases with alkali-metal ionic size while the one-dimensional [(Cr3As³)2-]∞ 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. [ABSTRACT FROM AUTHOR]