First-principles prediction of phonon-mediated superconductivity in XBC (X= Mg, Ca, Sr, Ba)

TL;DR

This paper predicts four new stable XBC compounds with potential high-temperature superconductivity, especially MgBC with a $T_c$ of 51 K, based on first-principles calculations of their electronic and phononic properties.

Contribution

The study introduces four novel intercalated hexagonal XBC compounds as stable, phonon-mediated superconductors, with detailed predictions of their critical temperatures and electron-phonon interactions.

Findings

MgBC has a predicted $T_c$ of 51 K.

Other compounds have $T_c$ between 4-17 K.

MgBC's high $T_c$ is due to strong electron-phonon coupling.

Abstract

From first-principles calculations, we predict four new intercalated hexagonal $X$BC ($X$=Mg, Ca, Sr, Ba) compounds to be dynamically stable and phonon-mediated superconductors. These compounds form a LiBC like structure but are metallic. The calculated superconducting critical temperature, $T{_c}$, of MgBC is 51 K. The strong attractive interaction between $\sigma$-bonding electrons and the B${_{1g}}$ phonon mode gives rise to a larger electron-phonon coupling constant (1.135) and hence high $T_c$; notably, higher than that of MgB$_2$. The other compounds have a low superconducting critical temperature (4-17 K) due to the interaction between $\sigma$-bonding electrons and low energy phonons (E${_{2u}}$ modes). Due to their energetic and dynamic stability, we envisage that these compounds can be synthesized experimentally.