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Register a new userSemiclassical theory of the circular photogalvanic effect in gyrotropic systems
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We develop a theory of circular photogalvanic effect (CPGE) for classically high photon energies which exceed the electron scattering rate but are small compared to the average electron kinetic energy. In this frequency range one can calculate the CPGE by using two different approaches. In the fully quantum-mechanical approach we find the photocurrent density by applying Fermis golden rule for indirect intraband optical transitions with virtual intermediate states both in the conduction and valence bands. In the framework of the semiclassical approach, we apply a generalized Boltzmann equation with accounts for the Berry-curvature induced anomalous velocity, side jumps and skew scattering. The calculation is carried out for a wurtzite symmetry crystal. Both methods yield the same results for the CPGE current demonstrating consistency between the two approaches and applicability of the semiclassical theory for the description of nonlinear high-frequency transport.
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We develop a semiclassical theory of nonlinear transport and the photogalvanic effect in non-centrosymmetric media. We show that terms in semiclassical kinetic equations for electron motion which are associated with the Berry curvature and side jumps give rise to a dc current quadratic in the amplitude of the ac electric field. We demonstrate that the circular photogalvanic effect is governed by these terms in contrast to the linear photogalvanic effect and nonlinear I-V characteristics which are governed mainly by the skew scattering mechanism. In addition, the Berry curvature contribution to the magnetic-field induced photogalvanic effect is calculated.
We have studied the circular photogalvanic effect (CPGE) in Cu/Bi bilayers. When a circularly polarized light in the visible range is irradiated to the bilayer from an oblique incidence, we find a photocurrent that depends on the helicity of light. Such photocurrent appears in a direction perpendicular to the light plane of incidence but is absent in the parallel configuration. The helicity dependent photocurrent is significantly reduced for a Bi single layer film and the effect is nearly absent for a Cu single layer film. Conventional interpretation of the CPGE suggests the existence of spin-momentum locked band(s) of a Rashba type in the Cu/Bi bilayer. In contrast to previous reports on the CPGE studied in other systems, however, the light energy used here to excite the carriers is much larger than the band gap of Bi. Moreover, the CPGE of the Cu/Bi bilayer is larger when the energy of the light is larger: the helicity dependent photocurrent excited with a blue light is nearly two times larger than that of a red light. We therefore consider the CPGE of the Cu/Bi bilayer may have a different origin compared to conventional systems.
We introduce the magnon circular photogalvanic effect enabled by stimulated Raman scattering. This provides an all-optical pathway to the generation of directed magnon currents with circularly polarized light in honeycomb antiferromagnetic insulators. The effect is the leading order contribution to magnon photocurrent generation via optical fields. Control of the magnon current by the polarization and angle of incidence of the laser is demonstrated. Experimental detection by sizeable inverse spin Hall voltages in platinum contacts is proposed.
The magneto-gyrotropic photogalvanic and spin-galvanic effects are observed in (0001)-oriented GaN/AlGaN heterojunctions excited by terahertz radiation. We show that free-carrier absorption of linearly or circularly polarized terahertz radiation in low-dimensional structures causes an electric photocurrent in the presence of an in-plane magnetic field. Microscopic mechanisms of these photocurrents based on spin-related phenomena are discussed. Properties of the magneto-gyrotropic and spin-galvanic effects specific for hexagonal heterostructures are analyzed.
The resonant circular photogalvanic effect is observed in wurtzite (0001)-oriented GaN low-dimensional structures excited by infrared radiation. The current is induced by angular momentum transfer of photons to the photoexcited electrons at resonant inter-subband optical transitions in a GaN/AlGaN heterojunction. The signal reverses upon the reversal of the radiation helicity or, at fixed helicity, when the propagation direction of the photons is reversed. Making use of the tunability of the free-electron laser FELIX we demonstrate that the current direction changes by sweeping the photon energy through the intersubband resonance condition, in agreement with theoretical considerations.
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