Superconductivity in the 2-Dimensional Homologous Series AMm Bi3 Q5+m (m=1, 2) (A=Rb, Cs; M=Pb, Sn; Q=Se, Te).

Superconductivity in the two-dimensional AMm Bi3 Q5+m family of semimetals is reported. The AMBi3 Te6 (m=1) and AM2 Bi3 Te7 (m=2) members of the homologous series with A=Rb, Cs and M=Pb, Sn undergo a bulk superconducting transition ranging from 2.7 to 1.4 K depending on the composition. The estimated superconducting volume fraction is about 90 %. Superconducting phase diagrams as a function of chemical pressure are constructed for the solid solution products of each member of the homologous series, AMBi3-x Sbx Te6-y Sey and AM2 Bi3-x Sbx Te7-y Sey (0≤x≤3 or 0≤y≤2). The structural flexibility of the ternary AMm M'3 Te5+m semiconducting homology to form isostructural analogues with a variety of metals, M=Pb, Sn; M'=Bi, Sb, gives access to a large number of electronic configurations and superconductivity due to chemical pressure effects.