Pumping approximately integrable systems

Area of Science:

• Quantum physics
• Many-body systems
• Statistical mechanics

Background:

• Weak perturbations can drive systems from equilibrium by utilizing protected degrees of freedom.
• This principle has enabled the creation of exotic condensates like those of photons and magnons.
• Integrable quantum systems possess infinite conservation laws, offering unique dynamics.

Purpose of the Study:

• To develop a theoretical framework for understanding weakly driven integrable quantum systems.
• To investigate the induction of spin and heat currents in these systems, even with integrability-breaking perturbations.
• To characterize the resulting steady states and their dependence on perturbation structure.

Main Methods:

• Development of a theory for weakly driven integrable systems.
• Analysis of how pumping activates local and quasi-local conserved quantities.
• Characterization of steady states using a truncated generalized Gibbs ensemble.

Main Results:

• Pumping can induce substantial spin and heat currents in weakly driven integrable systems.
• Integrability-breaking perturbations do not prevent current generation; they activate approximate conserved quantities.
• The steady state is described by a generalized Gibbs ensemble whose parameters depend on perturbation structure, not amplitude or initial state.

Conclusions:

• Weakly driven integrable systems offer a novel route to generating directed spin and heat transport.
• The concept of activating approximate conserved quantities is key to understanding these phenomena.
• Spin-chain materials driven by terahertz radiation are proposed as experimental platforms for integrability-based pumps.