Quantum many-body scars from magnon condensation

TLDR

Generic many‑body systems normally decohere and thermalize, but the emergence of quantum many‑body scarring in a far‑from‑equilibrium, strongly interacting system is striking and unexpected. The study seeks to explain quantum many‑body scarring and demonstrate that the proposed mechanism can be generalized to other systems. They propose that Bose‑Einstein condensation of magnons, where macroscopic numbers of quasiparticles occupy a single quantum state, underlies the scarring phenomenon. Numerical evidence supports that Bose‑Einstein condensation explains the observed quantum many‑body scarring.

Abstract

According to quantum statistical mechanics, generic many-body systems decohere and thermalize regardless of their initial state. A recent experiment found a surprising exception to this rule, wherein an otherwise thermalizing system maintains its coherence only for a particular initial condition, a phenomenon dubbed ``quantum many-body scarring.'' Here, the authors propose and provide numerical evidence for a physical mechanism underlying the observed phenomena: Bose-Einstein condensation, wherein macroscopic numbers of quasiparticles occupy a single quantum state. While this phenomenon is well known at equilibrium, its emergence in a strongly interacting, far-from-equilibrium system is striking and unexpected. The physical principle explored in this work can be applied to other systems to reveal new examples of quantum many-body scars.