Squeezed Ensembles and Anomalous Dynamic Roughening in Interacting Integrable Chains

Area of Science:

• Condensed Matter Physics
• Quantum Many-Body Systems
• Statistical Mechanics

Background:

• Isolated integrable quantum systems are expected to equilibrate to generalized Gibbs ensembles.
• Canonical thermalization describes the expected relaxation dynamics in such systems.

Purpose of the Study:

• To identify and characterize initial states in interacting integrable models that deviate from standard generalized thermalization.
• To investigate anomalous quantum transport and fluctuations in specific quantum states.

Main Methods:

• Analysis of the quantum XXZ chain in the easy-axis regime.
• Study of pure nonequilibrium initial states lacking magnetic fluctuations.
• Examination of relaxation dynamics and fluctuation properties.

Main Results:

• Nonfluctuating initial states relax to squeezed generalized Gibbs ensembles with subextensive charge fluctuations.
• At the isotropic point, relaxation from the Néel state exhibits extensive fluctuations and superdiffusive scaling (Kardar-Parisi-Zhang universality).
• Other nonfluctuating states, like spin singlets, show diffusive scaling.

Conclusions:

• Demonstrates a class of initial states evading canonical thermalization in integrable models.
• Highlights exotic equilibrium states with anomalous scaling and fluctuations.
• Provides experimentally testable predictions for cold atomic systems regarding quantum transport.