Bloch-Landau-Zener dynamics in single-particle Wannier-Zeeman systems

TL;DR

This paper explores the dynamics of Bloch oscillations and Landau-Zener tunneling in a spin-dependent periodic potential system, revealing how spin coupling influences adiabatic and non-adiabatic behaviors in Wannier-Zeeman systems.

Contribution

It introduces the concept of Bloch-Landau-Zener dynamics in Wannier-Zeeman systems and analyzes the effects of spin coupling on these phenomena.

Findings

Weak coupling leads to non-adiabatic dynamics.

Strong coupling results in adiabatic evolution.

Spatial Landau-Zener transitions occur due to spin-dependent forces.

Abstract

Stimulated by the experimental realization of spin-dependent tunneling via gradient magnetic field [Phys. Rev. Lett. 111, 225301 (2013); Phys. Rev. Lett. 111, 185301 (2013)], we investigate dynamics of Bloch oscillations and Landau-Zener tunneling of single spin-half particles in a periodic potential under the influence of a spin-dependent constant force. In analogy to the Wannier-Stark system, we call our system as the Wannier-Zeeman system. If there is no coupling between the two spin states, the system can be described by two crossing Wannier-Stark ladders with opposite tilts. The spatial crossing between two Wannier-Stark ladders becomes a spatial anti-crossing if the two spin states are coupled by external fields. For a wave-packet away from the spatial anti-crossing, due to the spin-dependent constant force, it will undergo spatial Landau-Zener transitions assisted by the intrinsic intra-band Bloch oscillations, which we call the Bloch-Landau-Zener dynamics. If the inter-spin coupling is sufficiently strong, the system undergoes adiabatic Bloch-Landau-Zener dynamics, in which the spin dynamics follows the local dressed states. Otherwise, for non-strong inter-spin couplings, the system undergoes non-adiabatic Bloch-Landau-Zener dynamics.