Spintronics in time-dependent systems: Manipulation and detection of spin currents by rashba spin-orbit interaction

Official URL: https://risc01.sabanciuniv.edu/record=b2993662_(Table of contents)

In this thesis, we focus on manipulating spin-orbit interaction to generate spin-dependent transport in two-dimensional electron gases (2DEG). Rashba spin-orbit interaction (SOI) can be modulated both spatially and temporally. Here, we explore how we can create spin currents in nano- or mesoscale conductors via periodically time-dependent Rashba SOI. We base our calculations on the Floquet scattering theory, which is the standard tool to study time dependent transport properties in these systems. In particular, we analyze AC and DC charge and spin currents generated by dynamical Rashba SOI in the absence of bias voltage, checking our analytical expressions and approximations with full numerical spin-dependent transport simulations and studying our numerical results in both low and high-frequency regimes. We also investigate high harmonic generation in a time-dependent Rashba coupling and study the pumping charge and spin current when the system involves one or two adjustable parameters in and beyond the adiabatic approximation. Spin-orbit coupling in 2DEGs can also be formulated using SU(2) gauge fields. Through an SU(2) gauge transformation, one can show that the time-dependent Rashba SOI induces spin-dependent voltages. Furthermore, this gauge transformation enables one to identify relevant Onsager symmetries. The latter can then be exploited for the realization of spin transistor devices, particularly when the spin-orbit interaction is inhomogeneous throughout the sample. Combining these two concepts, we propose a spin transistor that generates spin current by employing the dynamical SOI. Finally, we exploit spatially inhomogeneous Rashba SOI to convert spin currents into charge currents, providing an experimentally feasible detection mechanism.