Dynamic impurities in two-dimensional topological insulator-edge states

TL;DR

This paper investigates how periodically driven magnetic impurities affect the density of states and conductance in two-dimensional topological insulator edge states, revealing potential for impurity characterization.

Contribution

It introduces a Floquet Green's function approach to analyze dynamical impurity effects on topological insulator edges, highlighting how potential energy influences transport properties.

Findings

Increasing potential closes the DOS gap across all driving frequencies.

Transmission gap is also closed, with energy asymmetry.

Dynamical effects provide insights into magnetic impurity characteristics.

Abstract

Helical edge states of two-dimensional topological insulators show a gap in the density of states (DOS) and suppressed conductance in the presence of ordered magnetic impurities. Here we will consider the dynamical effects on the DOS and transmission when the magnetic impurities are driven periodically. Using the Floquet formalism and Green's functions, the system properties are studied as a function of the driving frequency and the potential energy contribution of the impurities. We see that increasing the potential part closes the DOS gap for all driving regimes. The transmission gap is also closed, showing a pronounced asymmetry as a function of energy. These features indicate that the dynamical transport properties could yield valuable information about the magnetic impurities.