Experimental Demonstration of Spin Geometric Phase: Radius Dependence of Time-Reversal Aharonov-Casher Oscillations

Abstract

A geometric phase of electron spin is studied in arrays of InAlAs/InGaAs two-dimensional electron gas rings. By increasing the radius of the rings, the time-reversal symmetric Aharonov-Casher oscillations of the electrical resistance are shifted towards weaker spin-orbit interaction regions with their shortened period. We conclude that the shift is due to a modulation of the spin geometric phase, the maximum modulation of which is approximately 1.5 rad. We further show that the Aharonov-Casher oscillations in various radius arrays collapse onto a universal curve if the radius and the strength of Rashba spin-orbit interaction are taken into account. The result is interpreted as the observation of the effective spin-dependent flux through a ring.

Spin-charge conversion in a multiterminal Aharonov-Casher ring coupled to precessing ferromagnets: A charge-conserving Floquet nonequilibrium Green function approach

“…1) can be controlled by the top-gate covering the ring, by the cone angle of precessing magnetization set by the input microwave power driving the precession, and by the setup geometry; (iii) to examine if the device setup in Fig. 1 can be used as a new playground for experiments 21,24,27,28 measuring charge currents to detect quantum interference effects involving AC phase in a single mesoscopic ring where multichannel effects in a typical ring of finite width act as effective dephasing (by entangling spin and orbital degrees of freedom 36 or averaging over orbital channels with different interference patterns 31 ), thereby randomizing interference patterns as in conventional measurements using dc bias voltage.…”

“…(23) and (24). Similarly, G < (t, t ′ ) can also be further simplified by taking advantages of relation (18) and change of variables.…”

“…24 For example, the destructive quantum interferences, controlled by the accumulated AC phase via tuning of the strength of the Rashba SOC (which depends on the applied top-gate voltage 25,26 ), cause un-polarized charge current injected into the two-terminal AC rings to diminish 24,[27][28][29][30][31] [to zero 31 if the ring is strictly one-dimensional (1D)]. Similarly, in four-terminal AC rings one encounters quantum-interference-controlled SHE, predicted in Ref.…”

Quantum Transport Phenomena Of Two-Dimensional Mesoscopic Structures

“…If we consider a multi-mode channel, the formula for the current I + reads 23) where the function M(E) provides us the number of modes that are below the cut-off energy E. Then, we assume that the number of modes M is constant over the energy range µ 1 > E > µ 2 , and at low temperature we find that 24) where (µ 1 − µ 2 )/e is the bias voltage. Thus the contact resistance is given by G…”

“…It has already been demonstrated in different nanosystems [20,21,22]. Control of the spin geometric phase in semiconductor quantum rings has also been demonstrated [23,24]. Nanocrystals, quantum boxes and quantum dots are semiconductor systems whose spatial extension usually ranges from 1 nm to 10 nm.…”