LAUSR

Abstract (A = K, Rb, Cs) are the unique Cr-based ambient-pressure superconductors discovered in 2015. The new superconducting family are structurally characterised by quasi one-dimensional (Q1D) [() double-walled subnanotubes. Peculiar properties have been revealed, which mostly point to unconventional superconductivity. In this contribution, we first describe how the superconductors were discovered. Then we overview recent progress on the crystal structure, electronic structures, theoretical models and physical properties in . Some new experimental results are included. Finally, we conclude by addressing the related open questions in this emerging subfield of superconductivity.