Voltage-controlled spin precession

Spin-transport properties of a lateral spin-valve structure originating from spin precession in its two-dimensional semiconducting channel under the influence of Rashba spin-orbit (RSO) coupling are explored. The effect of the finite extent of the injecting and detecting contact pads, along the length of the channel, on the spin signals is studied in these structures using (1) a simple theoretical treatment leading to analytical expressions for spin-dependent voltages derived using the stationary phase approximation, and (2) a more rigorous theoretical treatment based on nonequilibrium Green's function formalism to calculate these voltages, in a nonlocal spin-valve setup. Using both these approaches, it is found that the oscillation in spin voltages, which is observed by varying RSO when the magnetization directions of the injector and detector are parallel to the current flow, reduces in amplitude and shifts in phase for contact pads having finite length when compared to the corresponding results for a zero length (point-contact) limit. The amplitude and phase of the oscillation can be recovered to its point-contact limit if the RSO underneath the contacts is assumed to be zero. These models were compared against a recent experiment, and it is found that certain aspects of the experiment can be described well while some other aspects deserve further investigation. Factors that could have influenced the experiment and thereby could explain the discrepancy with the theory were analyzed. Conditions for observing Hanle oscillation in such a structure is discussed. Finally, the possibility of controlling the magnetization reversal via the gate is discussed, which could extend and quantify the 'Datta-Das' effect for voltage controlled spin-precession.