Superconductivity on ScH$_{3}$ and YH$_{3}$ hydrides: Effects of applied pressure in combination with electron- and hole-doping on the electron-phonon coupling properties

Abstract

The implementation of electron-and hole-doping, in conjunction to applied pressure, is analyzed as a mechanism to induce or enhance the superconducting state on fcc YH3 and ScH3. In particular, the evolution of their structural, electronic, and lattice dynamical properties, as well as the electron-phonon coupling and superconducting critical temperature (Tc) is presented and discussed, as a function of the electron-and hole-doping content as well as applied pressure. The study was performed within the density functional perturbation theory, taking into account the effects of zero-point energy through the quasi-harmonic approximation, while the doping was implemented by means of the construction of the Sc1−xMxH3 (M=Ca,Ti) and Y1−xMxH3 (M=Sr,Zr) solid solutions modeled with the virtual crystal approximation (VCA). We found that the ScH3 and YH3 hydrides shown a significant improvement of their electron-phonon coupling properties under hole-doping (M=Ca,Sr) and at pressure values close to dynamical instabilities. Instead, by electron-doping (M=Ti,Zr), the systems do not improve such properties, whatever value of applied pressure is considered. Then, as a result, Tc rapidly increases as a function of x on the hole-doping region, reaching its maximum value of 92.7(67.9) K and 84.5(60.2) K at x = 0.3 for Sc1−xCaxH3 at 10.8 GPa and Y1−xSrxH3 at 5.8 GPa respectively, with µ * = 0(0.15), while for both, electron-and hole-doping, Tc decreases as a function of the applied pressure, mainly due to phonon hardening. By the thorough analysis of the electron-phonon properties as a function of doping and pressure, we can conclude that the tuning of the lattice dynamics is a promising path for improving the superconductivity on both systems.