Superconductivity up to 14.2 K in MnB$_4$ under pressure

TL;DR

This paper reports the discovery of superconductivity up to 14.2 K in MnB4 under high pressure, revealing a pressure-induced transition and suggesting an unconventional pairing mechanism beyond BCS theory.

Contribution

It demonstrates superconductivity in a Mn-based compound under high pressure and explores its structural and electronic properties, highlighting a novel pathway for high-temperature superconductivity.

Findings

Superconductivity appears above 30 GPa in MnB4.

Maximum T_c of 14.2 K at 150 GPa.

Evidence of an unconventional pairing mechanism.

Abstract

The discovery of superconductivity in 3$d$-transition metal compounds with strong magnetism is interesting but rare. Especially for Mn-based compounds, there exist only very limited materials that show superconductivity. Here, we report the discovery of superconductivity up to 14.2 K in a Mn-based material MnB$_4$. By applying high pressures, we found the continuous suppression of a weak insulating behavior and the occurrence of superconductivity after about 30 GPa. With further increasing pressure, $T_\text{c}$ is gradually enhanced and reaches the maximum value of about 14.2 K at 150 GPa with a Fermi-Liquid behavior in the normal states. The synchrotron X-ray diffraction data reveal the unchanged monoclinic (S.G: $P2_1/c$) symmetry but an unusual crossover of the lattice parameters $b$ and $c$. Theoretical calculations based on the electron-phonon coupling picture reveal a very low $T_\text{c}$ (less than 1 K), manifesting an exotic pairing mechanism beyond the Bardeen-Cooper-Schrieffer (BCS) theory. Our findings show a promising way to explore high $T_\text{c}$ superconductivity by combining the 3d-transition metal magnetic elements and light elements.