SAIP2026

Understanding the Electronic Structure and Topological States of Bi₂Se₃ Material: Effects of SOC, van der Waal Interactions, and Hybrid Functional Corrections

7 Jul 2026, 17:20

1h 20m

Great Hall (University of the Western Cape)

Poster Presentation Track A - Physics of Condensed Matter and Materials Poster Session 1

Speaker

Beauty Masolo (University of Pretoria)

Description

Bi₂Se₃ is a three-dimensional topological material with distinct electronic properties, characterized by an insulating bulk and conducting surface states. These surface states are protected by time-reversal symmetry, making this material a promising candidate for quantum computing applications. Understanding the topological state of Bi₂Se₃ at the atomic level, and its ability to mitigate decoherence is crucial, as it may host the required Majorana states. In this study, the electronic state configurations of bulk Bi₂Se₃ were investigated using first-principles calculations within the framework of Density Functional Theory. It is observed that the generalized gradient approximation with the Perdew-Burke-Ernzerhof functional underestimates the band gap (~0.12 eV), whereas the inclusion of spin-orbit coupling (SOC) and van der Waals (vdW) corrections increases it to ~0.29 eV. This highlights the critical role of relativistic effects associated with heavy elements such as bismuth, as well as the weak interlayer coupling inherent to this layered material. Further corrections, although computationally expensive, were performed using the HSE + SOC + vdW approach, yielding a band gap closer to the experimental value of approximately ~0.32 eV. The surface state nature of the material was studied by varying the number of quantized layers (QLs) from 1 to 5. Dirac cone electronic states emerge at the Γ-point for 3-5 QLs, confirming the topological nature of the material. The non-trivial topology of Bi₂Se₃ was further verified through the calculation of Z₂ topological invariants using both the parity eigenvalue method at time-reversal invariant momenta and the Wilson loop formalism. The consistency between these methods demonstrates the robustness of the topological phase. These findings emphasize the crucial interplay among SOC, vdW interactions, and hybrid functional corrections in determining the electronic properties of Bi₂Se₃, and they lay the groundwork for its integration with superconducting systems, with potential applications in topological quantum computing.