Quantum rings with time dependent spin-orbit coupling: Rabi oscillations, spintronic Schrodinger-cat states, and conductance properties

TL;DR

This paper investigates the effects of periodically modulated spin-orbit coupling in quantum rings, revealing Rabi oscillations, spintronic Schrödinger-cat states, and dominant sideband conductance channels under realistic conditions.

Contribution

It introduces the concept of time-dependent spin-orbit coupling in quantum rings and analyzes resulting quantum phenomena and transport properties with potential spintronic applications.

Findings

Rabi oscillations occur in weak spin-orbit coupled rings.

Collapse and revival phenomena in wave packet evolution.

Sideband currents can dominate conductance despite disturbances.

Abstract

The strength of the (Rashba-type) spin-orbit coupling in mesoscopic semiconductor rings can be tuned with external gate voltages. Here we consider the case of a periodically changing spin-orbit interaction strength as induced by sinusoidal voltages. In a closed one dimensional quantum ring with weak spin-orbit coupling, Rabi oscillations are shown to appear. We find that the time evolution of initially localized wave packets exhibits a series of collapse and revival phenomena. Partial revivals -- that are typical in nonlinear systems -- are shown to correspond to superpositions of states localized at different spatial positions along the ring. These "spintronic Schrodinger-cat sates" appear periodically, and similarly to their counterparts in other physical systems, they are found to be sensitive to environment induced disturbances. The time dependent spin transport problem, when leads are attached to the ring, is also solved. We show that the "sideband currents" induced by the oscillating spin-orbit interaction strength can become the dominant output channel, even in the presence of moderate thermal fluctuations and random scattering events.