Anomalous Pressure Dependence of the Superconducting Transition Temperature in TlNi${}_2$Se${}_{2-x}$S${}_x$

Abstract

We report the pressure dependence of the superconducting transition temperature, $T_c$, in TlNi${}_2$Se${}_{2-x}$S${}_x$ detected via the AC susceptibility method. The pressure-temperature phase diagram constructed for TlNi${}_2$Se${}_2$, TlNi${}_2$S${}_2$ and TlNi${}_2$SeS exhibits two unexpected features: (a) a sudden collapse of the superconducting state at moderate pressure for all three compositions and (b) a dome-shaped pressure dependence of $T_c$ for TlNi${}_2$SeS. These results point to the nontrivial role of S substitution and its subtle interplay with applied pressure, as well as novel superconducting properties of the TlNi${}_2$Se${}_{2-x}$S${}_x$ system.

4 pages, 3 figures