High-$T_{\rm c}$ Ag$_x$BC and Cu$_x$BC superconductors accessible via topochemical reactions

TL;DR

This study predicts that metastable Ag$_x$BC and Cu$_x$BC phases, accessible through topochemical reactions, can be high-temperature superconductors with unique electronic properties, expanding the landscape of superconducting materials.

Contribution

It introduces a new class of metastable layered borocarbide superconductors accessible via topochemical reactions, with potential for high-temperature superconductivity.

Findings

AgBC exhibits two-gap superconductivity above 50 K.

Metastable AgBC and CuBC phases can be synthesized from Li$_x$BC.

Predicted materials are metallic, unlike known borocarbides.

Abstract

Hole-doping of covalent materials has long served as a blueprint for designing conventional high-$T_{\rm c}$ superconductors, but thermodynamic constraints severely limit the space of realizable compounds. Our ab initio results indicate that metastable Ag$_x$BC and Cu$_x$BC phases can be accessed via standard topochemical ion exchange reactions starting from Li$_x$BC precursors. Unlike all known stoichiometric layered metal borocarbides, the predicted AgBC and CuBC derivatives, comprising honeycomb layers bridged by dumbbells, are metallic rather than semiconducting. Anisotropic Migdal-Eliashberg analysis reveals that the intrinsically hole-doped AgBC possesses a unique combination of electronic and vibrational features to exhibit two-gap superconductivity above 50 K.