Singlet s±-wave pairing in quasi-one-dimensional ACr₃As₃ (A=K, Rb, Cs) superconductors

The recent discovery of quasi-1D Cr-based superconductivity has generated much excitement. We study in this work the superconducting instabilities of a representative compound, the newly synthesized KCr₃As₃ superconductor. Based on inputs from DFT calculations, we first construct an effective multi-orbital TB Hamiltonian to model its low-energy band structure. We then employ standard RPA calculations to investigate the superconducting instabilities of the resultant multi-orbital Hubbard model. We find the leading pairing symmetry realized in this material is singlet s±-wave pairing. This singlet pairing is driven by spin-density wave fluctuations enhanced by FS. We design a phase-sensitive measurement to identify the s-wave pairing. The s±-wave pairing in KCr₃As₃ shall also exhibit a subgap spin resonance mode near the nesting vector, which can be tested by inelastic neutron scattering measurements. We also propose further application of KCr₃As₃ by utilizing it to induce TRI TSC via proximity effect. Our study shall be of general relevance to all superconductors in the family of ACr₃As₃ (A=K, Rb, Cs). Reference: arXiv: 1809.07117