Dynamic localization in optical and Zeeman lattices in the presence of spin-orbit coupling

TL;DR

This study investigates how spin-orbit coupling influences dynamic localization of a two-level atom in optical and Zeeman lattices, revealing resonance conditions, spin oscillations, and effects of band structure on localization.

Contribution

It provides a detailed analysis of resonance phenomena and spin dynamics in spin-orbit coupled lattices, highlighting conditions for localization and the impact of band crossing and higher harmonics.

Findings

Resonance frequencies are determined by the band structure and affected by spin-orbit coupling.

Pseudo-resonances are independent of potential type and spin-orbit strength, but involve significant dispersion.

Spin-orbit coupling can suppress wavepacket oscillations in optical lattices.

Abstract

The dynamic localization of a two-level atom in a periodic potential under the action of spin-orbit coupling and a weak harmonically-varying linear force is studied. We consider optical and Zeeman potentials that are either in-phase or out-of-phase in two spinor components, respectively. The expectation value for the position of the atom after one oscillation period of the linear force is recovered in authentic resonances or in pseudo-resonances. The frequencies of the linear force corresponding to authentic resonances are determined by the band structure of the periodic potential and are affected by the spin-orbit coupling. The width/dispersion of the wavepacket in authentic resonances is usually minimal. The frequencies corresponding to pseudo-resonances do not depend on the type of potential and on the strength of the spin-orbit coupling, while the evolution of excitations at the corresponding frequencies is usually accompanied by significant dispersion. Pseudo-resonances are determined by the initial phase of the linear force and by the quasi-momentum of the wavepacket. Due to the spinor nature of the system, the motion of the atom is accompanied by periodic, but not harmonic, spin oscillations. Under the action of spin-orbit coupling the oscillations of the wavepacket can be nearly completely suppressed in optical lattices. Dynamic localization in Zeeman lattices is characterized by doubling of the resonant oscillation periods due to band crossing at the boundary of the Brillouin zone. We also show that higher harmonics in the Fourier expansion of the energy band lead to effective dispersion, which can be strong enough to prevent dynamic localization of the Bloch wavepacket.