Pumping approximately integrable systems

TL;DR

This paper develops a theory showing that weak driving can induce large currents in approximately integrable quantum systems by activating near-conserved quantities, leading to novel steady states.

Contribution

It introduces a framework for understanding weakly driven integrable systems and demonstrates how pumping activates approximate conserved quantities to sustain large currents.

Findings

Pumping can induce large spin and heat currents in integrable systems.

Steady states are described by a truncated generalized Gibbs ensemble.

Potential experimental realization using spin-chain materials driven by terahertz radiation.

Abstract

Weak perturbations can drive an interacting many-particle system far from its initial equilibrium state if one is able to pump into degrees of freedom approximately protected by conservation laws. This concept has for example been used to realize Bose-Einstein condensates of photons, magnons, and excitons. Integrable quantum systems, like the one-dimensional Heisenberg model, are characterized by an infinite set of conservation laws. Here we develop a theory of weakly driven integrable systems and show that pumping can induce large spin or heat currents even in the presence of integrability breaking perturbations, since it activates local and quasi-local approximate conserved quantities. The resulting steady state is qualitatively captured by a truncated generalized Gibbs ensemble with Lagrange parameters that depend on the structure but not on the overall amplitude of perturbations nor the initial state. We suggest to use spin-chain materials driven by terahertz radiation to realize integrability-based spin and heat pumps.