Coherent Dynamics of the Off-Diagonal Spin-Boson Model in the Ultra-Strong Coupling Regime

TL;DR

This paper explores the complex transient dynamics of the off-diagonal spin-boson model under ultra-strong coupling, revealing how hybrid interactions induce localization and enable persistent quantum coherence.

Contribution

It provides new insights into the off-diagonal spin-boson model's dynamics in the ultra-strong coupling regime, highlighting the role of hybrid interactions and localization effects.

Findings

Localization induced by hybrid system-bath interactions

Persistence of quantum coherence at ultra-strong coupling

Separation of timescales in non-equilibrium dynamics

Abstract

Quantum mechanics describes the unitary time evolution of closed systems. In practice, every quantum system interacts with the environment leading to an irreversible loss of coherence. The Spin-Boson model (SBM) is central to the understanding of the fundamental process of decoherence of a two-state quantum system interacting with a bosonic heat bath but the nature of transient dynamics in the presence of hybrid diagonal and off-diagonal system-bath interactions remains largely unexplored. Here, we investigate how the hybrid system-bath interactions of an Ohmic environment induce localization in the bias-free SBM. For strong coupling to the environment, localization is strongly affected by a dynamically generated bias via the renormalization of the tunneling amplitude. We find that counteractive effects of Hamiltonian parameters on non-exponential short-time dynamics and long-time population equilibration can lead to a separation of timescales and non-equilibrium quantum coherent dynamics that can persist even for ultra-strong system-bath interaction. The findings offer novel opportunities to exploit coherence as a resource in quantum devices operating in the ultra-strong coupling regime.