Origin of band inversion in topological Bi2Se3

Stephen Chege,Patrick Ning’I,George O Amolo,James Sifuna

doi:10.1063/5.0022525

Stephen Chege, Patrick Ning’I + Show 2 more

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https://doi.org/10.1063/5.0022525

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Abstract

Topological materials and more so insulators have become ideal candidates for spintronics and other novel applications. These materials portray band inversion that is considered to be a key signature of topology. It is not yet clear what drives band inversion in these materials and the basic inferences when band inversion is observed. We employed a state-of-the-art ab initio method to demonstrate band inversion in topological bulk Bi2Se3 and subsequently provided a reason explaining why the inversion occurred. From our work, a topological surface state for Bi2Se3 was described by a single gap-less Dirac cone at k→ = 0, which was essentially at the Γ point in the surface Brilloiun zone. We realized that band inversion in Bi2Se3 was not entirely dependent on spin–orbit coupling as proposed in many studies but also occurred as a result of both scalar relativistic effects and lattice distortions. Spin–orbit coupling was seen to drive gap opening, but it was not important in obtaining a band inversion. Our calculations reveal that Bi2Se3 has an energy gap of about 0.28 eV, which, in principle, agrees well with the experimental gap of ≈0.20 eV–0.30 eV. This work contributes to the understanding of the not so common field of spintronics, eventually aiding in the engineering of materials in different phases in a non-volatile manner.

Highlights

We appreciate the fact that topological materials form a broad class of materials ranging from insulators,[1] superconductors,[2] and semi-metals.[3]
We have demonstrated the fundamental band inversion in topological Bi2Se3, which is a result of both scalar relativistic and fully relativistic effects
Our work indicates a critical role played by spin–orbit coupling in such materials on the opening of the band structure

Summary

Introduction

We appreciate the fact that topological materials form a broad class of materials ranging from insulators,[1] superconductors,[2] and semi-metals.[3]. As we focus on novel topological insulators, it is important to shed light on their intrinsic character. These insulators are characterized by a Hamiltonian that is not, in any way, adiabatically connected to the atomic limit. This implies that when tuning external parameters to change the Hamiltonian, the process is extremely slow such that the material remains in the ground state throughout.[7] A typical example of the atomic limit may be a case of diamond

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