Physics (Internal)

Transport in Dirac materials exposed to strong electromagnetic radiation

This event is part of the Condensed Matter Theory Seminar Series.

Abstract: We study transport in materials with Dirac quasiparticle dispersion (such as graphene, Weyl semimetal, the surface of a 3D topological insulator) in the presence of linearly-polarised electromagnetic radiation of very large intensity. We demonstrate that low-energy dynamics in such materials can be described by an effective time-independent Hamiltonian, characterised by multiple Dirac points in the first Brillouin zone. Around each Dirac point the spectrum is anisotropic: the velocity along the polarisation of the radiation significantly exceeds the velocity in the perpendicular direction. Moreover, at some Dirac points the transverse velocity oscillates as a function of the radiation intensity. These features of the spectrum manifest themselves in transport phenomena in the presence of a strong electromagnetic radiation. For instance, the conductance of a graphene p-n junction in the regime of strong irradiation depends on the polarisation as $G(\theta)\propto|\sin\theta|^{3/2}$, where $\theta$ is the angle between the polarisation and the p-n interface, and oscillates as a function of the radiation intensity.