Phase Transition and Field Effect Topological Quantum Transistor made of monolayer MoS2

TL;DR

This paper investigates topological phase transitions in monolayer MoS2, demonstrating its potential as a field effect topological quantum transistor through theoretical modeling and conductance calculations.

Contribution

It introduces a two-band Hamiltonian model for MoS2, revealing non-trivial topology and valley-dependent properties, and shows how the material can function as a topological quantum transistor.

Findings

Identification of QAH, QSH, and SQAH phases in MoS2

Non-zero valley Chern number indicating non-trivial topology

Demonstration of transistor behavior via conductance calculations

Abstract

We study topological phase transitions and topological quantum field effect transistor in monolayer Molybdenum Disulfide (MoS2) using a two-band Hamiltonian model. Without considering the quadratic (q^2) diagonal term in the Hamiltonian, we show that the phase diagram includes quantum anomalous Hall (QAH), quantum spin Hall (QSH), and spin quantum anomalous Hall effect (SQAH) regions such that the topological Kirchhoff law is satisfied in the plane. By considering the q^2 diagonal term and including one valley, it is shown that MoS2 has a non-trivial topology, and the valley Chern number is non-zero for each spin. We show that the wave function is (is not) localized at the edges when the q^2 diagonal term is added (deleted) to (from) the spin-valley Dirac mass equation. We calculate the quantum conductance of zigzag MoS2 nanoribbons by using the nonequilibrium Green function method and show how this device works as a field effect topological quantum transistor.