Anomalous-circular photogalvanic effect in a GaAs/AlGaAs two-dimensional electron gas

Abstract

We have studied the circular photogalvanic effect (CPGE) in a GaAs/AlGaAs two-dimensional electron gas excited by near infrared light at room temperature. The anomalous CPGE observed under normal incidence indicates a swirling current which is realized by a radial spin current via the reciprocal spin-Hall effect. The anomalous CPGE exhibits a cubic cosine dependence on the incidence angle, which is discussed in line with the above interpretation.

Observation of Extrinsic Photo-Induced Inverse Spin Hall Effect in a GaAs/AlGaAs Two-Dimensional Electron Gas

“…where J PISHE is the PISHE current excited by left-hand circular polarization light, L 1 and L 2 are the photocurrent induced by linearly polarized light, and J 1 is the background current [ 19 ]. It should be noted that the L 2 term has been included in the fitting equation, i.e., Eq.…”

“…The spin-to-charge current conversion in semiconductors is an important issue, since it open an avenue to integrate spintronics with electronics [ 5 ]. Photo-induced ISHE (PISHE) is recently emerging as an effective experimental tool to investigate the ISHE in semiconductors, which exploits a circularly polarized light with a Gaussian distribution to introduce a spin current into semiconductors and then utilizes the ISHE to generate a charge current [ 2 , 19 – 22 ]. The PISHE current can be observed at room temperature, and it offers a convenient way to investigate the ISHE of semiconductors without introducing magnetic field and ferromagnetic elements [ 20 ].…”

“…Besides, the PISHE also paves a way to design new kinds of spin-photonics devices [ 22 ]. The PISHE current has been observed in GaN/AlGaN, GaAs/AlGaAs, and MgZnO/ZnO heterostructures [ 2 , 19 , 20 ]. However, the dependence of the PISHE current on the light power and light profile is still unknown.…”

Anomalous circular photogalvanic effect of the spin-polarized two-dimensional electron gas in Mg0.2Zn0.8O/ZnO heterostructures at room temperature

“…However, a mechanism which can generate SRPC at normal incidence had been reported. 18,19 This effect was named anomalous CPGE (ACPGE) and generated by the radial spin current induced by the gradient of the spin polarization distribution through RSHE. The ACPGE current has an antisymmetric spatial distribution, which is largest at normal incidence, and decreases with increasing the incident angle.…”

“…3(a). 18,19 We can write these two terms as nðrÞ ¼ n 0 ð1 À f ðrÞÞ and s z ðrÞ ¼ p Á f ðrÞ Á cos h r , respectively, where f ðrÞ is the probability of excitation at r, p ¼ 1/2 represents the angular momentum taken by one excited electron, and h r is the corresponding refraction angle. The existence of cos h r in the second term bases on the fact that only the polarization in z direction could contribute to the ACPGE.…”