Global Quenches after Localized Perturbations

Area of Science:

• Quantum physics
• Condensed matter physics
• Many-body systems

Background:

• Investigating quantum systems after a global quench is crucial for understanding their dynamics.
• The behavior of spin-1/2 chains under perturbations is a key area in condensed matter theory.
• Translational invariance is a fundamental property in many physical systems.

Purpose of the Study:

• To examine the long-term effects of a localized perturbation (a single spin flip) on quantum spin chains.
• To determine if translational invariance is restored after a global quench following a spin flip.
• To explore the underlying mechanisms, potentially topological, responsible for persistent localized effects.

Main Methods:

• Simulating spin-1/2 chains with local Hamiltonians.
• Introducing a single spin flip as a localized perturbation before a global quench.
• Analyzing the system's behavior in the infinite-time limit.

Main Results:

• The localized perturbation's effect persists regardless of distance from the initial spin flip.
• Translational invariance is not restored in the system after the quench.
• The infinite-time state depends on whether the initial spin was flipped or not.

Conclusions:

• Localized perturbations in translationally invariant quantum systems can have non-decaying effects.
• The phenomenon suggests a breakdown of ergodicity or thermalization due to the perturbation.
• Topological properties, specifically semilocal charges, are conjectured to be the cause of this persistent behavior.