Suppression of gapless edge states in interaction driven topological insulators

• Main Author: Thayalan Raman
• Other Authors: Pinaki Sengupta
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Science::Physics::Atomic physics::Solid state physics
• Online Access: https://hdl.handle.net/10356/157023
• Institution: Nanyang Technological University

A topological insulator is a special class of material where the bulk of the material is gaped, exhibiting insulating properties, and the edges are gapless, exhibiting behaviours of a conductor due to one unpaired electron. This report seeks to investigate if there is any suppression of gapless edge states when lattice interactions are considered. These conditions were then simulated at ground state in an open-boundary, one-dimensional extended Peierls-Hubbard model at half-filling. A numerical method by the name of stochastic series expansion, a branch of Quantum Monte Carlo methods, is used to run the simulations for finite length models. The model considers electron-electron interactions and a finite range of electron-phonon coupling parameters. Firstly, spin stiffness is used as an indicator to observe the transition to Peierls state at ground temperature for closed boundary conditions at a critical phonon coupling value. This provides details about the critical phonon coupling values. Choosing an appropriate phonon coupling value based on the previous details, a comparison between odd length and even length chains were done at open boundary conditions. It was found that there is always suppression of gapless edge states for both even and odd length chain of sites.