Pressure induced superconductivity in WB2 and ReB2 through modifying the B layers

TL;DR

This study demonstrates that applying high pressure induces superconductivity in WB2, with a maximum Tc of 15 K, and explores how boron layer geometry influences superconductivity in transition-metal diborides.

Contribution

It provides the first systematic investigation of pressure effects on WB2 and ReB2, revealing pressure-induced superconductivity in WB2 and highlighting the importance of boron layer geometry.

Findings

Superconductivity in WB2 appears above 60 GPa with Tc up to 15 K.

No superconductivity was observed in ReB2 within the studied pressure range.

Structural phases of WB2 and ReB2 remain stable under high pressure.

Abstract

The recent discovery of superconductivity up to 32 K in the pressurized MoB2 reignites the interests in exploring high-Tc superconductors in transition-metal diborides. Inspired by that work, we turn our attention to the 5d transition-metal diborides. Here we systematically investigate the responses of both structural and physical properties of WB2 and ReB2 to external pressure, which possess different types of boron layers. Similar to MoB2, the pressure-induced superconductivity was also observed in WB2 above 60 GPa with a maximum Tc of 15 K at 100 GPa, while no superconductivity was detected in ReB2 in this pressure range. Interestingly, the structures at ambient pressure for both WB2 and ReB2 persist to high pressure without structural phase transitions. Theoretical calculations suggest that the ratio of flat boron layers in this class of transition-metal diborides may be crucial for the appearance of high Tc. The combined theoretical and experimental results highlight the effect of geometry of boron layers on superconductivity and shed light on the exploration of novel high-Tc superconductors in borides.