Crystal Symmetry, Strain, and Facet-Dependent Nature of Topological Surface States in Mercury Selenide

Daniel Dumett Torres, Sudhakar Pamidighantam, Prashant K. Jain

Research output: Contribution to journalArticlepeer-review

Abstract

Spin-filtered surface conduction channels set topological insulator (TI) materials apart as a distinct class and grant them physical properties that are suited to the discovery of new quantum phenomena and advanced applications such as topological quantum computing. Even though high-throughput band structure investigations have uncovered new TI materials, it remains to be verified whether surface states of these TI materials exhibit spin-momentum locking, a property thought to be essential for long spin lifetimes of carriers required for spintronics and manifestation of exotic quantum particles. To this end, we examined using density functional theory the spin-resolved surface electronic structures of mercury selenide (HgSe). HgSe exists in a natural zinc-blende phase (zb-HgSe) with no crystal anisotropy and a non-natural wurtzite phase (wz-HgSe), which has an inherent anisotropy along the {001}h direction. Both phases have an inverted band structure. However, while zb-HgSe is a gapless semimetal, we find that wz-HgSe exhibits, due to its crystal anisotropy, a bulk band gap making it a three-dimensional (3D) TI. We show that wz-HgSe exhibits surface states with spin-momentum locking on its {001}h facets, which are normal to the anisotropy axis. Furthermore, we find that zb-HgSe can be converted from a semimetal to a 3D TI through the opening of a bulk band gap by the application of uniaxial strain along specific crystallographic axes. However, only the {111}c facets of zb-HgSe, which are analogous to the {001}h facets of wz-HgSe, exhibit surface states with spin-momentum locking, whereas the {001}c facets of zb-HgSe do not. This work provides new insight into the structural aspects that determine the spin texture of surface states. Spin-momentum locking is exhibited only on specific surface facets, depending on the crystallographic symmetry, the presence and direction of inherent anisotropy, or the presence of applied uniaxial strain.

Original languageEnglish (US)
Pages (from-to)10344-10352
Number of pages9
JournalJournal of Physical Chemistry C
Volume124
Issue number19
DOIs
StatePublished - May 14 2020

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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