Fermionic transport through a driven quantum point contact: breakdown of Floquet thermalization beyond a critical driving frequency

TL;DR

This paper investigates how a driven quantum point contact between fermionic chains can cause a breakdown of Floquet thermalization at high frequencies, leading to persistent particle imbalance and halted current, challenging existing thermalization theories.

Contribution

It demonstrates the breakdown of Floquet eigenstate thermalization in a fermionic system with a driven QPC at a critical frequency, supported by numerical simulations across protocols and interactions.

Findings

Current halts above a critical frequency

Particle imbalance remains indefinitely

Breakdown of Floquet eigenstate thermalization

Abstract

We study a quantum system that consists of two fermionic chains coupled by a driven quantum point contact (QPC). The QPC contains a bond with a periodically varying tunneling amplitude. Initially the left chain is packed with fermions while the right one is empty. We numerically track the evolution of the system and demonstrate that, at frequencies above a critical one, the current through the QPC halts, and the particle imbalance between the chains remains forever. This implies a spectacular breakdown of the Floquet version of the eigenstate thermalization hypothesis which predicts a homogeneous particle density profile at large times. We confirm the effect for various driving protocols and interparticle interactions.