Metal Borohydrides as high-$T_{c}$ ambient pressure superconductors

TL;DR

This paper proposes a novel method to achieve high-temperature superconductivity at ambient pressure by doping metal borohydrides, specifically Ca(BH4)2, using first-principles calculations to demonstrate potential $T_c$ values around 110 K.

Contribution

It introduces a new doping strategy in metal borohydrides to realize high-$T_c$ superconductivity at ambient conditions, bypassing high-pressure requirements.

Findings

Doping Ca(BH4)2 with 0.03 holes per formula unit yields $T_c$ up to 110 K.

Strong electron-phonon coupling in doped borohydrides facilitates high-temperature superconductivity.

Doping can be achieved without significant electronic structure disruption and at moderate energetic costs.

Abstract

The extreme pressures required to stabilize the recently discovered superhydrides represent a major obstacle to their practical application. In this paper, we propose a novel route to attain high-temperature superconductivity in hydrides at ambient pressure, by doping commercial metal borohydrides. Using first-principles calculations based on Density Functional Theory and Migdal-Eliashberg theory, we demonstrate that in Ca(BH$_4$)$_2$ a moderate hole doping of 0.03 holes per formula unit, obtained through a partial replacement of Ca with monovalent K, is sufficient to achieve $T_c$'s as high as 110 K. The high-$T_c$ arises because of the strong electron-phonon coupling between the B-H $\sigma$ molecular orbitals and bond-stretching phonons. Using a random sampling of large supercells to estimate the local effects of doping, we show that the required doping can be achieved without significant disruption of the electronic structure and at moderate energetic cost. Given the wide commercial availability of metal borohydrides, the ideas presented here can find prompt experimental confirmation. If successful, the synthesis of high-$T_c$ doped borohydrides will represent a formidable advancement towards technological exploitation of conventional superconductors.