Transport properties in a two-dimensional Su-Schrieffer-Heeger model in Quantum Hall Regime

TL;DR

This study explores how a two-dimensional Su-Schrieffer-Heeger model behaves under a magnetic field, revealing phase transitions, localized states, and the role of edge modes in transport within the quantum Hall regime.

Contribution

It introduces a detailed analysis of the 2D SSH model's transport properties in a magnetic field using NEGF, highlighting phase transitions and Landau level formation.

Findings

Transition from gapped to flat band regime with magnetic field

Emergence of localized states at zero energy

Edge modes facilitate ballistic transport along edges

Abstract

We investigate the transport properties of a two-dimensional Su-Schrieffer-Heeger (2D SSH) model in the quantum Hall regime using non-equilibrium Green's function formalism (NEGF). The device Hamiltonian, where the 2D SSH model serves as the channel, is constructed using a nearest-neighbor tight-binding model. The effect of an external perpendicular magnetic field is incorporated into the contacts via Peierls substitution. We observe a transition from a gapped phase to a flat band regime at zero energy by varying the magnetic field. This transition is characterized by the emergence of highly localized states in the bulk or edges, which we observe by calculating local density-of-states (LDOS). We analyze transport in the system along two directions ($x$ and $y$) via transmission measurements, indicating a magnetic field-induced transition from insulating to metallic phase. The study of the energy spectrum of the system shows the formation of Landau levels. Moreover, the quantum number of the non-degenerate and degenerate Landau levels (transmission modes) can be any integer or only an odd integer, depending on diagonal, inter-cell, and intra-cell hopping strengths. From the analysis of the transport properties along $y$-direction, we find that edge modes play a crucial role in facilitating ballistic transport.