Helicity dependent photocurrent in electrically gated (Bi,Sb)_2Te_3 thin films

Abstract

Circularly polarized photons are known to generate a directional helicity-dependent photocurrent in three-dimensional topological insulators at room temperature. Surprisingly, the phenomenon is readily observed at photon energies that excite electrons to states far above the spin-momentum locked Dirac cone and the underlying mechanism for the helicity-dependent photocurrent is still not understood. We resolve the puzzle through a comprehensive study of the helicity-dependent photocurrent in (Bi,Sb)_2Te_3 thin films as a function of the incidence angle of the optical excitation, its wavelength, and the gate-tuned chemical potential. Our observations allow us to unambiguously identify the circular photo-galvanic effect as the dominant mechanism for the helicity-dependent photocurrent. Additionally, we use an analytical calculation to relate the directional nature of the photocurrent to asymmetric optical transitions between the topological surface states and bulk bands. The insights we obtain are important for engineering opto-spintronic devices that rely on optical steering of spin and charge currents.

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• Spin-momentum locked interaction between guided photons and surface electrons in topological insulators
• Circular photogalvanic effect in Cu/Bi bilayers
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• Tailoring Photocurrent in Weyl Semimetals via Intense Laser Irradiation
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• Ultrafast dynamics of photocurrents in surface states of 3D topological insulators
• Interface enhanced helicity dependent photocurrent in metal/semimetal bilayers
• Reversible Engineering of Topological Insulator Surface State Conductivity through Optical Excitation
• Giant inverse Faraday effect in Dirac semimetals
• Band Structure and Polarization Effects in Photothermoelectric Spectroscopy of a Bi2Se3 Device
• Generation and manipulation of chiral terahertz waves emitted from the three-dimensional topological insulator Bi2Te3
• Visible and Terahertz Nonlinear Responses in the Topological Noble Metal Dichalcogenide PdTe2
• Controlling helicity-dependent photocurrent in polycrystalline Sb${}_2$Te${}_2$Se topological insulator thin films at ambient temperature through wave-vector of and photothermal gradient due to polarized light
• Transverse Photoresistivity from Photothermal Current Deflection in Metal Films
• Enhanced detection of circularly polarized photons with topological materials