Quantum interference control of currents in CdSe with a single optical beam

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Abstract
We show that ballistic current generation can occur in a semiconductor via quantum interference between absorption pathways for orthogonal polarization components of a single-frequency beam. This effect occurs for a subset of noncentrosymmetric materials, is macroscopically associated with a second-order nonlinear optical susceptibility, and produces current injection linearly proportional to the beam intensity. We demonstrate this in wurtzite CdSe (Eg=1.75 eV) at 295 K using cw and femtosecond optical sources of wavelength 600–750 nm (2.07–1.66 eV). The intensity and spectral dependence are in reasonable agreement with a first-principles calculation. Continuous current density of 30 μA cm−2 is produced for 60 mW cm−2 intensity at 633 nm.