R. Cuan | Searcharxiv

arXiv2015

Quantum transport properties in Datta-Das tuned opacity spin-transistors

We studied the spin-dependent quantum transport properties using a simple modelling of a Datta-Das spin transistor. We refine previous results by accounting the propagation medium changes of opacity felt by itinerant electrons, when the gate-voltage is switched on and modelling them via the transversal energy levels mismatch. Monitoring the topological-dependent conductance, we are able to identify the device operating points. If the incoming electrons energy approaches the biased-induced barriers height, the spin-resolved conductance oscillations become significant. In a zero temperature picture, our computations of the spin-dependent conductance as function of the electric field at the region below the gate electrode suggest the feasibility of the modeled device. Although we demonstrate that phase time may not be spin-resolved, our simulation allows us to evaluate the time that takes an electron to experience a spin-flip process, resulting in an order of magnitude lower than typical values of the spin relaxation times.

cond-mat.mes-hall↗

arXiv2015

Rashba-coupling modelling for two-dimensional and high-order Rashba Hamiltonian for one-dimensional confined heavy holes

Based on standard k.p (8 x 8) multiband Hamiltonian, we have deduced an explicit analytical expression for the Rashba-coupling parameter which clarifies its anomalous behavior for heavy holes (hh), gated in quasi-two-dimensional (Q2D) systems, by letting grow the density. Our modelling remarkable better agrees with experimental results in comparison with earlier theoretical models, while recovers the expected cubic dependence on the quasi-momentum. For quasi-one-dimensional (Q1D) hh systems, we have formally derived an effective Rashba Hamiltonian with two competitive terms on the quasi-momentum, a linear term and a cubic one as predicted from suitable approximations to the Q2D scope. The Rashba-coupling parameters also behave anomalously and qualitatively support recent experiments in core/shell nanowires. Furthermore, they exhibit an essential asymptotic discontinuity in the low density regime as a function of the lateral confinement length. For hh, we present closed schemes to accurately quote the Rashba-coupling parameters both for the Q2D and Q1D systems, which become unprecedented for holes.

cond-mat.mes-hall↗