A first-principles study of superconductivity on RbH by doping without applied pressure

TL;DR

This study demonstrates that electron-doping in RbH via Sr substitution enhances superconductivity, achieving critical temperatures up to 66.1 K without external pressure, by analyzing electronic and phononic properties through first-principles calculations.

Contribution

It provides a systematic first-principles analysis showing how electron-doping induces superconductivity in RbH without applied pressure, highlighting the role of Sr-content in tuning properties.

Findings

Superconducting critical temperature reaches 66.1 K at high Sr-content.

Electron-doping increases electron-phonon coupling constant to 1.92.

Metallization and phonon softening drive the rise in superconductivity.

Abstract

The structural, electronic, lattice dynamics, electron-phonon coupling, and superconducting properties of the alkali-metal hydride RbH, metalized through electron-doping by the construction of the solid-solution Rb$_{1-x}$Sr$_x$H, are systematically analyzed as a function of Sr-content within the framework of density functional perturbation and Migdal-Eliashberg theories, taking into account the effect of zero-point energy contribution by the quasi-harmonic approximation. For the entire studied range of Sr-content, steady increments of the electron-phonon coupling constant and the superconducting critical temperature are found with progressive alkaline-earth metal content through electron-doping, reaching the values of $\lambda=1.92$ and $T_c=51.3(66.1)$~K with $\mu^*$=0.1(0). The steady rise of such quantities as a function of Sr-content is consequence of the metallization of the hydride as an increase of density of states at the Fermi level is observed, as well as the softening of the phonon spectrum, mainly coming from H-optical modes. Our results indicate that electron-doping on metal-hydrides is an encouraging alternative to look for superconductivity without applied pressure.