Magnetic field induced symmetry breaking in nonequilibrium quantum networks

TL;DR

This paper investigates how magnetic fields can break symmetries in nonequilibrium quantum networks, affecting transport properties and steady states, with implications for engineered quantum systems.

Contribution

It demonstrates the controllability of open-system symmetries via magnetic field orientation and explores the resulting effects on steady states and transport in cubic quantum networks.

Findings

Magnetic field direction can systematically break symmetries in quantum networks.

Symmetry breaking influences nonequilibrium steady states and transport properties.

Different environmental interactions lead to novel features in large cubic networks.

Abstract

We study the effect of an applied magnetic field on the nonequilibrium transport properties of a general cubic quantum network described by a tight-binding Hamiltonian with specially designed couplings to the leads that preserve open-system symmetries. We demonstrate that the symmetry of open systems can be manipulated by the direction of the magnetic field. Starting with all the symmetries preserved in absence of a field, the anisotropic and isotropic fields systematically break the symmetries, influencing all nonequilibrium properties. For simple cubic systems, we are able to identify the steady states that comprise of pure states, bath-dependent states (nonequilibrium steady states), and also nonphysical states. As an application, we show numerically for large cubic networks that the symmetry breaking can control nonequilibrium currents and that different environmental interactions can lead to novel features which can be engineered in artificial super-lattices and cold atoms.