Emergence of topological phase and non-trivial surface states in rare-earth semimetal GdSb with pressure

Abstract

We studied the evolution of band topology with external pressure in rare-earth GdSb using first-principles calculations. This material crystallizes in a rocksalt-type structure and shows the structural phase transition to CsCl-type structure at 26.1 GPa. The phonon dispersions are analyzed to ascertain the dynamical stability of this material. We used the hybrid density functional theory with the inclusion of spin-orbit coupling to investigate the structural, electronic, and topological phase transitions. At ambient pressure, GdSb shows a topologically trivial state which agrees with the existing experimental reports. The first topological phase transition is observed at 6 GPa of hydrostatic pressure (at the high symmetry X-point) verified with the help of single band inversions and surface states analysis along the (001) plane. The non-zero value of the first Z2 topological invariant and the presence of the Dirac cone also confirm the topological phase of this material. Further, an increase in pressure to 12 GPa, two band inversions, at Γ- as well as X-points, are observed which corresponds to the trivial nature of GdSb. The same is verified with (0;000) values of Z2 topological invariants and a pair of Dirac cones in surface states. It is noted that the crystal symmetries are preserved throughout the study and topological phase transition values are much lower than structural phase transition pressure i.e., 26.1 GPa.