Abstract
Bi 2 Se 3 , a layered three-dimensional (3D) material, exhibits topological insulating properties due to the presence of surface states and a bandgap of 0.3 eV in the bulk. We study the effect of hydrostatic pressure P and doping with rare earth elements on the topological aspect of this material in bulk from a first principles perspective. Our study shows that under a moderate pressure of P>7.9GPa, the bulk electronic properties show a transition from an insulating to a Weyl semi-metal state due to band inversion. This electronic topological transition may be correlated to a structural change from a layered van der Waals material to a 3D system observed at P=7.9GPa. At large P, the density of states have a significant value at the Fermi energy. Intercalating Gd with a small doping fraction between Bi2Se3 layers drives the system to a metallic anti-ferromagnetic state, with Weyl nodes below the Fermi energy. At the Weyl nodes, time reversal symmetry is broken due to the finite local field induced by large magnetic moments on Gd atoms. However, substituting Bi with Gd induces anti-ferromagnetic order with an increased direct bandgap. Our study provides novel approaches to tune topological transitions, particularly in capturing the elusive Weyl semimetal states, in 3D topological materials.
Highlights
Topological insulators (TIs) have potential future application in quantum computers[1,2,3] and spintronics[4,5,6] owing to the existence of symmetry protected edge or surface states and provide a fundamental bridge between high-energy and condensed-matter physics due to the presence of exotic physical states in the system
We study the effect of hydrostatic pressure P and doping with rare earth elements on the topological aspect of this material in bulk from a first principles perspective
The primary feature of the TI state is the inverted band structure, which results from the crossing of the valence and conduction bands of different parity symmetry,[13,14] and BixSb1Àx family of materials are a prime example of three-dimensional (3D) materials with Z2 invariant symmetry
Summary
Topological insulators (TIs) have potential future application in quantum computers[1,2,3] and spintronics[4,5,6] owing to the existence of symmetry protected edge or surface states and provide a fundamental bridge between high-energy and condensed-matter physics due to the presence of exotic physical states in the system. The material shows an electronic topological transition from a small bulk bandgap insulator at low HP, to a gapless dirac state at a critical pressure of 7.9 GPa, and to a WSM beyond the critical pressure. While intercalating Gd between the quintuple layers (QLs) shows a broad bandwidth metallic ground state, with a time reversal symmetry broken Weyl like feature in the band structure below the Fermi energy, substituting Bi with Gd shows an increase in bandgap and an insulating state.
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