Superconductivity and fluctuations in misfit layer compounds (MS) nTS 2

Abstract

Critical field data of the highly two-dimensional misfit layer materials (MS) n TS 2, M = Sn, Pb, Bi, La, Sm; T = Ta, Nb, are discussed together with earlier results from specific heat and AC susceptibility measurements. All materials become superconducting above 70 mK, except for M = La,Sm. Compounds with M = Sn, Pb; T = Ta, Nb behave as anisotropic 3-D BCS superconductors with small coherence lengths, whereas (BiS) 1.08TaS 2 shows large two-dimensional fluctuations below 1 K. Below 0.78 K the system becomes 3-D. CDW formation and concomittant charge fluctuations in the BiS layer might explain this effect.