Pressure effect on the superconducting and the normal state of β − B i 2 Pd

The pressure effect up to 24.0 kbar on superconducting and normal-state properties of $\beta -B{i}_2\mathrm{Pd}$single crystal ($T_c\approx 4.98K$ at ambient pressure) has been investigated by measurements of the electrical resistivity. In addition, we have performed the heat capacity measurements in the temperature range 0.7–300 K at ambient pressure. The recent calculations of electronic density of states, electron-phonon interaction spectral function, and phonon density of states of $\beta -B{i}_2\mathrm{Pd}$ [Zheng and Margine, Phys. Rev. B 95, 014512 (2017)], are used to fit the resistivity and the heat capacity data. In the superconducting state we have focused on the influence of pressure on the superconducting transition temperature $T_c$ and upper critical field $H_{c2}$ and a negative effect with $d{T}_c/dp=–0.025K/\mathrm{kbar}$ and $d{H}_{c2}/dp=–8\mathrm{mT}/\mathrm{kbar}$ is found. A simplified Bloch-Grüneisen model was used to analyze the pressure effect on the temperature dependence of the normal-state resistivity. The obtained results point to a decrease of the electron-phonon coupling parameter λ and to a shift of phonon frequencies to higher values with pressure. Moreover, the temperature dependence of the normal-state resistivity follows a $T^2$ dependence above $T_c$ up to about 25 K. Together with the enhanced value of Sommerfeld coefficient $\gamma =13.23\mathrm{mJ}\mathrm{mo}{l}^{-1}{K}^{-2}$ these results point to a certain role of the electron-electron interaction in the superconducting pairing mechanism in $\beta -B{i}_2\mathrm{Pd}$.