Quantum walks accompanied by spin flipping in one-dimensional optical lattices

TL;DR

This paper studies how spin-flipping affects quantum walks of two fermions in one-dimensional optical lattices, revealing a spin-flipping induced localization linked to a flat band, with potential experimental implications.

Contribution

It demonstrates the emergence of spin-flipping induced localization in quantum walks due to a flat band, and explores control via Zeeman field and interaction effects.

Findings

Spin-flipping causes localization in quantum walks.

Ramping Zeeman field restores linear expansion.

Flat band underpins the localization phenomenon.

Abstract

We investigate continuous-time quantum walks of two fermionic atoms loaded in one-dimensional optical lattices with on-site interaction and subjected to a Zeeman field. The quantum walks are accompanied by spin-flipping processes. We calculate the time-dependent density distributions of the two fermions with opposite spins which are initially positioned on the center site by means of exact numerical method. Besides the usual fast linear expansion behavior, we find an interesting spin-flipping induced localization in the time-evolution of density distributions. We show that the fast linear expansion behavior could be restored by simply ramping on the Zeeman field or further increasing the spin-flipping strength. The intrinsic origin of this exotic phenomenon is attributed to the emergence of a flat band in the single particle spectrum of the system. Furthermore, we investigate the effect of on-site interaction on the dynamics of the quantum walkers. The two-particle correlations are calculated and signal of localization is also shown therein. A simple potential experimental application of this interesting phenomenon is proposed.