Weyl Semimetallic Phase in High Pressure CrSb$_2$ and Structural Compression Studies of its High Pressure Polymorphs

TL;DR

This paper investigates high-pressure phases of CrSb2, revealing a Weyl semimetallic phase in the MoP2-type polymorph through structural and electronic analysis, with implications for discovering new Weyl semimetals.

Contribution

It provides the first confirmation of the MoP2-type structure in CrSb2 and demonstrates its Weyl semimetallic properties under high pressure.

Findings

MoP2-type CrSb2 is a Weyl semimetal with type-I Weyl points.

No phase transitions observed up to 50 GPa for CuAl2-type and 40 GPa for MoP2-type.

MoP2-type phase is less compressible despite lower coordination number.

Abstract

In this study, high pressure synchrotron powder X-ray diffraction is used to investigate the compression of two high pressure polymorphs of \ce{CrSb2}. The first is the \ce{CuAl2}-type polymorph with an eight-fold coordinated Cr, which can be quenched to ambient conditions from high-pressure high-temperature conditions. The second is the recently discovered \ce{MoP2}-type polymorph, which is induced by compression at room temperature, with a seven-fold coordinated Cr. Here, the assigned structure is unambiguously confirmed by solving it from single-crystal X-ray diffraction. Furthermore, the electrical properties of the \ce{MoP2}-type polymorph were investigated theoretically and the resistance calculations under pressure were accompanied by resistance measurements under high pressure on a single crystal of \ce{CrSb2}. The calculated electronic band structure for the \ce{MoP2}-type phase is discussed and we show that the polymorph is semimetallic and possesses type-I Weyl points. No further phase transitions were observed for the \ce{CuAl2}-type structure up to 50 GPa and 40 GPa for the \ce{MoP2}-type structure. Even though the \ce{CuAl2}-phase has the highest coordination number of Cr, it was found to be less compressible than the \ce{MoP2}-phase having a seven-fold coordinated Cr, which was attributed to the longer Cr-Sb distance in the \ce{CuAl2}-type phase. The discovery of a type-I Weyl semimetallic phase in \ce{CrSb2} opens up for discovering other Weyl semimetals in the transition metal di-pnictides under high pressure.