Inducing anisotropies in Dirac fermions by periodic driving

TL;DR

This paper investigates how periodic driving fields can induce anisotropies and quasienergy gaps in the Dirac fermions of Bi$_2$Se$_3$, a topological insulator, using high-frequency expansions and numerical simulations.

Contribution

It provides analytical and numerical analysis of how periodic driving modifies the Dirac cone in a topological insulator, revealing anisotropies and energy gaps.

Findings

Periodic driving induces anisotropies in Dirac fermions.

A quasienergy gap opens under in-plane elliptically polarized fields.

Analytical results agree with numerical simulations.

Abstract

We consider the three-dimensional Hamiltonian for Bi$_2$Se$_3$, a second-generation topological insulator, under the effect of a periodic drive for both in-plane and out-of-plane fields. As it will be shown by means of high-frequency expansions up to second order in the Floquet Hamiltonian, the driving induces anisotropies in the Dirac cone and opens up a quasienergy gap for in-plane elliptically polarized fields. Analytic expressions are obtained for the renormalized velocities and the quasienergy gap. These expressions are then compared to numerical calculations performed by discretizing the Hamiltonian in a one-dimensional lattice and following a staggered fermion approach, achieving a remarkable agreement. We believe our work may have an impact on the transport properties of topological insulators.