Topological phase transition and tunable surface states in YBi

TL;DR

This study uses hybrid density functional theory to explore the topological phase transitions in YBi, revealing pressure and strain-induced changes from trivial to non-trivial topological states, which could link to its large magnetoresistance.

Contribution

It provides detailed theoretical insights into the pressure and strain-induced topological phase transitions in YBi, a material with large magnetoresistance, clarifying its topological nature.

Findings

YBi is topologically trivial at ambient conditions.

Topological phase transitions occur at 6.5 GPa pressure and 3% strain.

Non-trivial topological states are characterized by band inversions near the Fermi level.

Abstract

A unique co-existence of extremely large magnetoresistance (XMR) and topological characteristics in non-magnetic rare-earth monopnictides stimulating intensive research on these materials. Yttrium monobismuthide (YBi) has been reported to exhibit XMR up to 105% but its Topological properties still need clarification. Here we use the hybrid density functional theory to probe the structural, electronic and topological properties of YBi in detail. We observe that YBi is topologically trivial semimetal at ambient pressure which is in accordance with reported experimental results. The topological phase transitions i.e., trivial to non-trivial are obtained with volumetric pressure of 6.5 GPa and 3% of epitaxial strain. This topological phase transitions are well within the structural phase transition of YBi (24.5 GPa). The topological non-trivial state is characterized by band inversions among Y-d band and Bi-p band near {\Gamma}- and X-point in the Brillouin zone. This is further verified with the help of surface band structure along (001) plane. The Z2 topological invariants are calculated with the help of product of parities and evolution of Wannier charge centers. The occurrence of non-trivial phase in YBi with a relatively small epitaxial strain, which a thin film geometry can naturally has, might make it an ideal candidate to probe inter-relationship between XMR and non-trivial topology.