Symmetry breaking and circular photogalvanic effect in epitaxial Cd${}_x$Hg${}_{1-x}$Te films

Abstract

We report on the observation of symmetry breaking and the circular photogalvanic effect in Cd${}_x$Hg${}_{1-x}$Te alloys. We demonstrate that irradiation of bulk epitaxial films with circularly polarized terahertz radiation leads to the circular photogalvanic effect (CPGE) yielding a photocurrent whose direction reverses upon switching the photon helicity. This effect is forbidden in bulk zinc-blende crystals by symmetry arguments, therefore, its observation indicates either the symmetry reduction of bulk material or that the photocurrent is excited in the topological surface states formed in a material with low Cadmium concentration. We show that the bulk states play a crucial role because the CPGE was also clearly detected in samples with non-inverted band structure. We suggest that strain is a reason of the symmetry reduction. We develop a theory of the CPGE showing that the photocurrent results from the quantum interference of different pathways contributing to the free-carrier absorption (Drude-like) of monochromatic radiation.

arXiv comment11 pages, 7 figures

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Cited by in corpus (7)

• Semiclassical theory of the circular photogalvanic effect in gyrotropic systems
• Optical response of two-dimensional Dirac materials with a flat band
• Photocurrents induced by structured light
• Optical properties of two dimensional Dirac Weyl materials with a flatband
• Transport properties of a 1000-nm HgTe film: the interplay of surface and bulk carriers
• Magnetophotogalvanic Effects Driven by Terahertz Radiation in CdHgTe Crystals with Kane Fermions
• Positive Terahertz Photoconductivity in CdHgTe Under Hydrostatic Pressure