Superconductivity and disorder effect in TlNi2Se2−xSx compounds

Abstract

After our first discovery of multi-band superconductivity (SC) in the TlNi2Se2 crystal, we successfully grew a series of TlNi2Se2−xSx () single crystals. Measurements of resistivity, specific heat, and susceptibility were carried out on these crystals. Superconductivity with K was first observed in the TlNi2S2 crystal, which also appears to involve heavy electrons with an effective mass –, as inferred from the normal state electronic specific heat and the upper critical field, . It was found that bulk SC and heavy-electron behavior is preserved in all the studied TlNi2Se2−xSx samples. In the mixed state, a novel change of the field dependence of the residual specific heat coefficient, , occurs in TlNi2Se2−xSx with increasing S content. We also found that the value changes with the disorder degree induced by the partial substitution of S for Se, characterized by the residual resistivity ratio (RRR). Thus, the TlNi2Se2−xSx system provides a platform to study the effect of disorder on the multi-band SC.