Pressure-induced high temperature superconductivity in H3X (X=As, Se, Br, Sb, Te and I)

Abstract

The discovery of high critical temperature T_{c} superconductivity in highly compressed H_{3}S has opened up the question of searching for strong electron-phonon coupling in the hydrides outside the transition metal series. The specific objective of this work is to explore the possibility of discovering a material that exceeds the superconducting transition temperature of H_{3}S. Our study includes the materials H_{3}X (X=As, Se, Br, Sb, Te, and I), is limited to the Im\overline{3}m crystal structure. The procedure we adopt involves performing linearized augmented plane wave calculations for many different volumes to compute the electronic densities of states and their pressure variation. This is combined with Quantum-ESPRESSO calculations from which we obtain the phonon frequencies and the electron-phonon coupling constant \lambda, and followed by applying the multiple scattering-based theory of Gaspari and Gyorffy to obtain the Hopfield parameters and the McMillan-Allen-Dynes theory. It should be stressed that the GG approach decouples the electronic contribution to \lambda from the corresponding phonon contribution, and provides additional insights for the understanding of superconductivity in these materials. Based on our analysis, the hydrogen is the main contributor to the T_{c} in these materials as it makes up 75\sim80 % of the total \lambda. Our calculations for H_{3}Se and H_{3}Br give a T_{c}{}{}\sim100 K. For the other materials in our study we find that H_{3}As is unstable and H_{3}Sb, H_{3}Te and H_{3}I have small values of the McMillan-Hopfield paramters which makes it unlikely to give high T_{c}. However, according to both of our rigid band model and virtual crystal calculations, we predict a T_{c}\sim150 K for H_{3}Br with a small amount of hydrogen doping.