Mao-Wang Lu

Structurally controllable spin spatial splitter in a hybrid ferromagnet and semiconductor nanostructure

We theoretically investigate modulation of a tunable δ-potential to the lateral displacement of electrons across a magnetically modulated semiconductor nanostructure. Experimentally, this nanostructure can be produced by depositing a nanosized ferromagnetic stripe with in-plane magnetization on top of a semiconductor heterostructure, while the δ-potential can be realized by means of the atomic layer doping technique. Theoretical analysis reveals that this δ-doping can break the intrinsic symmetry in nanostructure and a considerable spin polarization in the lateral displacement will appear. Numerical calculations demonstrate that both magnitude and sign of spin polarization can be manipulated by changing the height and/or position of the δ-doping, giving rise to a structurally tunable spin spatial splitter.

Manipulable GMR Effect in a δ-Doped Magnetically Confined Semiconductor Heterostructure

A giant magnetoresistance (GMR) device formed by depositing two parallel nanosized ferromagnetic strips on top of a semiconductor heterostructure has been proposed theoretically (Zhai etxa0al. in Phys Rev B 66:125305, 2002). For the sake of manipulating its performance, we introduce a tunable δ-potential into this device with the help of atomic-layer doping techniques such as molecular beam epitaxy (MBE) or metal-organic chemical-vapor deposition. We investigate theoretically the impact of such δ-doping on the magnetoresistance ratio (MR) of the GMR device. We find that, although the δ-doping is embedded in the device, a considerable GMR effect still exists due to the significant difference in electronic transmission between parallel (P) and antiparallel (AP) configurations. Moreover, the calculated results show that the MR of the GMR device varies sensitively with the weight and/or position of the δ-doping. Thus, the GMR device can be controlled by changing the δ-doping to obtain an adjustable GMR device for magnetoelectronics applications.

Spin filtering in a δ-doped magnetic-electric-barrier nanostructure

We report a theoretical study on spin-polarized transport in a δ-doped magnetic-electric-barrier nanostructure, which can be realized in experiments by depositing two ferromagnetic stripes on top and bottom of a semiconductor heterostructure under an applied voltage and by using atomic layer doping technique. The spin-polarized behavior of the electron in this device is found to be quite sensitive to the δ-doping. One can conveniently tune the degree of the electron spin polarization by adjusting the weight and/or position of the δ-doping. Thus, the involved nansosystem can be employed as a controllable spin filter, which may be helpful for exploiting new spin-polarized source for spintronics applications.

Effect of Rashba and Dresselhaus Spin–Orbit Couplings on Electron Spin Polarization in a Hybrid Magnetic–Electric Barrier Nanostructure

A theoretical study has been carried out on the spin-dependent electron transport in a hybrid magnetic–electric barrier nanostructure with both Rashba and Dresselhaus spin–orbit couplings, which can be experimentally realized by depositing a ferromagnetic strip and a Schottky metal strip on top of a semiconductor heterostructure. The spin–orbit coupling-dependent transmission coefficient, conductance, and spin polarization are calculated by solving the Schrödinger equation exactly with the help of the transfer-matrix method. We find that both the magnitude and sign of the electron spin polarization vary strongly with the spin–orbit coupling strength. Thus, the degree of electron spin polarization can be manipulated by properly adjusting the spin–orbit coupling strength, and such a nanosystem can be employed as a controllable spin filter for spintronics applications.