Edge photocurrent driven by terahertz electric field in bilayer graphene

We report on the observation of edge electric currents excited in bilayer graphene by terahertz laser radiation. We show that the current generation belongs to the class of second order in electric field phenomena and is controlled by the orientation of the THz electric field polarization plane. Additionally, applying a small magnetic field normal to the graphene plane leads to a phase shift in the polarization dependence. With increasing the magnetic field strength, the current starts to exhibit 1/B-magneto-oscillations with a period consistent with that of the Shubnikov-de Haas effect and amplitude by an order of magnitude larger as compared to the current at zero magnetic field measured under the same conditions. The microscopic theory developed shows that the current is formed in the edge's vicinity limited by the mean-free path of carriers and the screening length of the high-frequency electric field. The current originates from the alignment of the free carrier momenta and dynamic accumulation of charge at the edges, where the P-symmetry is naturally broken. The observed magneto-oscillations of the photocurrent are attributed to the formation of Landau levels

Terahertz laser radiation induced optoelectronic phenomena in HgTe-based topological insulators and graphene

The present thesis is aimed to the study of nonlinear optoelectronic phenomena induced by terahertz radiation in topological insulators and graphene. Within this work, the observation of new phenomena are presented, which provide a useful tool to study characteristic material properties. These include: cyclotron resonance of surface states in topological insulators, edge photocurrents in mono- and bi-layer graphene, resonant edge photocurrents in bi-layer graphene and a circular Hall effect in the absence of a magnetic field

Edge currents driven by terahertz radiation in graphene in quantum Hall regime

We observe that the illumination of unbiased graphene in the quantum Hall regime with polarized terahertz laser radiation results in a direct edge current. This photocurrent is caused by an imbalance of persistent edge currents, which are driven out of thermal equilibrium by indirect transitions within the chiral edge channel. The direction of the edge photocurrent is determined by the polarity of the external magnetic field, while its magnitude depends on the radiation polarization. The microscopic theory developed in this paper describes well the experimental data