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

摘要

Single crystals of A2Cr3As3 (A = K, Rb) were successfully grown using aself-flux method and studied via structural, transport and thermodynamicmeasurement techniques. The superconducting state properties between the twospecies are similar, with critical temperatures of 6.1 K and 4.8 K in K2Cr3As3and Rb2Cr3As3, respectively. However, the emergence of a strong normal stateelectronic anisotropy in Rb2Cr3As3 suggests a unique electronic tuningparameter 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 isconsistent with the proposed quasi-one-dimensional character of band structureand its evolution with alkali metal species in this new family ofsuperconductors.