$Ab~initio$ study of Li-Mg-B superconductors

TL;DR

This study predicts that LiB, a recently synthesized layered compound, could have a superconducting critical temperature exceeding 32 K when analyzed with anisotropic models, and explores related materials with potentially higher $T_c$ values.

Contribution

The paper provides the first anisotropic Migdal-Eliashberg calculations for LiB, revealing higher $T_c$ estimates, and identifies metastable Li-Mg-B phases with promising superconducting properties.

Findings

LiB may have a $T_c$ over 32 K based on anisotropic calculations.

Metastable Li-Mg-B phases could surpass MgB$_2$ in $T_c$.

Lower-pressure synthesis routes for LiB are suggested.

Abstract

LiB, a predicted layered compound analogous to the MgB$_2$ superconductor, has been recently synthesized via cold compression and quenched to ambient pressure, yet its superconducting properties have not been measured. According to prior isotropic superconductivity calculations, the critical temperature ($T_{\rm{c}}$) was expected to be only 10$-$15 K. Using the anisotropic Migdal-Eliashberg formalism, we show that the $T_{\rm{c}}$ may actually exceed 32 K. Our analysis of the contribution from different electronic states helps explain the detrimental effect of pressure and doping on the compound's superconducting properties. In the search for related superconductors, we screened Li-Mg-B binary and ternary layered materials and found metastable phases with $T_{\rm{c}}$ close to or even 10$-$20% above the record 39 K value in MgB$_2$. Our reexamination of the Li-B binary phase stability reveals a possible route to synthesize the LiB superconductor at lower pressures readily achievable in multianvil cells.