Superconductivity on ScH3 and YH3 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 with 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, including 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 showed 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 10.8GPa and Y1−xSrxH3 at 5.8GPa 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 superconductivity on both systems.