Effect of pressure on the superconducting properties of Au substituted PdTe$_2$ with the CdI$_2$-type structure

Abstract

Transition metal ditellurides with the CdI2-type structure are materials with intriguing superconducting and electronic properties as demonstrated by PdTe2. Gold substituted PdTe2, AuxPd1-xTe2, adopts the CdI2-type structure for a Pd content larger than 43 at.% at room temperature, and in this range enhanced superconductivity with a critical temperature (Tc) above 4 K has been reported (Kudo et al., PRB 93, 140505, 2016). Here we present the effect of pressure on the structural and superconducting properties of AuxPd1-xTe2 for x=0.15, 0.25 and 0.35 with Tc =2.7, 4.1, and 4.6 K at 1 atm, respectively. Synchrotron radiation x-ray diffraction shows that the CdI2-type structure remains stable up to 8 GPa for all three compositions and that they have almost the same volume compressibility. Heat capacity measurements show that Au substituted PdTe2 exhibits type-II superconductivity, that evolves from weak-coupling BCS for x = 0.15 to strong-coupling for x = 0.25 and 0.35. Electrical resistivity measurements up to a pressure of 2.5 GPa show that Tc(P) for x = 0.25 and 0.35 passes through a shallow maximum of 4.2 and 4.7 K at P ~ 0.3 and 0.7 GPa, respectively, compared to the monotonic decrease for x = 0.15. Furthermore, the pressure variation of the superconducting H - T phase diagram at each composition indicates that the superconducting properties remain essentially unchanged with pressure. The composition dependence of $T_{\rm c}$ is discussed by comparing the experimental results of AuxPd1-xTe2 to those of undoped PdTe2.