We demonstrate a spin pump to generate pure spin current of tunable intensity and polarization in the absence of charge current. The pumping functionality is achieved by means of an ac gate voltage that modulates the Rashba constant dynamically in a local region of a quantum channel with both static Rashba and Dresselhaus spin-orbit interactions. Spin-resolved Floquet scattering matrix is calculated to analyze the whole scattering process. Pumped spin current can be divided into spinpreserved transmission and spin-flip reflection parts. These two terms have opposite polarization of spin current and are competing with each other. Our proposed spin-based device can be utilized for non-magnetic control of spin flow by tuning the ac gate voltage and the driving frequency.

Electron carrier concentration dependent magnetization and transport properties in ZnO:Co diluted magnetic semiconductor thin films Exchange coupling between two magnetic films separated by an antiferromagnetic spacer

The optical properties of type-II ZnMnSe∕ZnSeTe multiple quantum wells were investigated by photoluminescence (PL) measurement. It was found that the peak position of PL spectra shows a giant blueshift under a moderate optical excitation level. The giant blueshift can be interpreted in terms of the band-bending effect due to the spatially photoexcited carriers in a type-II alignment. We also found that the PL spectra exhibit a large in-plane polarization with respect to ⟨110⟩ axis with the polarization degree up to 12.4%. We showed that the polarization does not depend on the excitation intensity as well as temperature, which excludes the possibility of extrinsic mechanisms related to the in-plane anisotropy. The observed anisotropic effects of ZnMnSe∕ZnSeTe multiple quantum wells were attributed to the intrinsic property of the orientation of chemical bonds at the heterointerface of the type-II band alignment.