Dissipative Yao-Lee Spin-Orbital Model: Exact Solvability and $\mathcal{PT}$ Symmetry Breaking

TL;DR

This paper introduces an exactly solvable dissipative spin-orbital model that reveals a PT symmetry breaking transition and hosts a rich spectrum of non-equilibrium steady states, advancing understanding of open quantum systems.

Contribution

It presents a novel, exactly solvable anisotropic Yao-Lee spin-orbital model with dissipation, mapping Liouvillian dynamics to non-Hermitian fermionic systems and analyzing PT symmetry breaking.

Findings

Identifies an exponentially large manifold of non-equilibrium steady states.

Discovers an exceptional ring in the Liouvillian spectrum in momentum space.

Maps out a PT symmetry breaking transition driven by dissipation.

Abstract

Exactly solvable dissipative models provide an analytical tool for studying the relaxation dynamics in open quantum systems. In this work, we study an exactly solvable model based on an anisotropic variant of the Yao-Lee spin-orbital model, with dissipation acting in the spin sector. We map Liouvillian dynamics to fermions hopping in a doubled Hilbert space under a non-Hermitian Hamiltonian and demonstrate the model's exact solvability. We analyze the model's strong and weak symmetries, which protect an exponentially large manifold of non-equilibrium steady states, establishing the system as a physically feasible dissipative spin liquid. Furthermore, we analyze the transient dynamics in a translationally invariant sector and discover that the single-particle Liouvillian spectrum hosts an exceptional ring in momentum space. We map out a characteristic $\mathcal{PT}$ symmetry breaking transition driven by the dissipation strength, which governs the crossover from oscillatory to decaying relaxation of physical observables. Our work provides a physically motivated, solvable setting for exploring the coexistence of dissipative spin liquid physics and Liouvillian spectral singularities.