A linearly polarized light normally incident on a semiconductor quantum wellwith spin-orbit coupling may generate pure spin current via direct interbandoptical transition. An electric photocurrent can be extracted from the purespin current when an in-plane magnetic field is applied, which has beenrecently observed in the InGaAs/InAlAs quantum well [Dai et al., Phys. Rev.Lett. 104, 246601 (2010)]. Here we present a theoretical study of thismagnetoelectric photocurrent effect associated with the interband transition.By employing the density matrix formalism, we show that the photoexcitedcarrier density has an anisotropic distribution in k space, strongly dependenton the orientation of the electron wavevector and the polarization of thelight. This anisotropy provides an intuitive picture of the observed dependenceof the photocurrent on the magnetic field and the polarization of the light. Wealso show that the ratio of the pure spin photocurrent to the magnetoelectricphotocurrent is approximately equal to the ratio of the kinetic energy to theZeeman energy, which enables us to estimate the magnitude of the pure spinphotocurrent. The photocurrent density calculated with the help of ananisotropic Rashba model and the Kohn-Luttinger model can produce all threeterms in the fitting formula for measured current, with comparable order ofmagnitude, but discrepancies are still present and further investigation isneeded.
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