Strongly anisotropic Dirac quasiparticles in irradiated graphene

TL;DR

This paper investigates how intense linearly-polarized light alters the quasiparticle behavior in graphene, creating anisotropic Dirac points and polarization-dependent conductance oscillations, revealing new control mechanisms for electronic properties.

Contribution

It introduces an effective Hamiltonian with multiple anisotropic Dirac points in irradiated graphene, showing polarization-dependent conductance and oscillations as a novel phenomenon.

Findings

Anisotropic Dirac spectrum with velocity anisotropy around each Dirac point.

Conductance of graphene p-n junction depends on polarization as |sinθ|^{3/2}.

Conductance oscillates with radiation intensity.

Abstract

We study quasiparticle dynamics in graphene exposed to a linearly-polarized electromagnetic wave of very large intensity. Low-energy transport in such system can be described by an effective time-independent Hamiltonian, characterized by multiple Dirac points in the first Brillouin zone. Around each Dirac point the spectrum is anisotropic: the velocity along the polarization of the radiation significantly exceeds the velocity in the perpendicular direction. Moreover, in some of the points the transverse velocity oscillates as a function of the radiation intensity. We find that the conductance of a graphene p-n junction in the regime of strong irradiation depends on the polarization as $G(\theta)\propto|\sin\theta|^{3/2}$, where $\theta$ is the angle between the polarization and the p-n interface, and oscillates as a function of the radiation intensity.