Localized systems coupled to small baths: from A$_{nderson}$ to Z$_{eno}$

TL;DR

This paper studies how coupling an Anderson localized system to a small, discrete-spectrum bath affects localization, revealing a non-monotonic relationship where weak coupling enhances transport and strong coupling induces a Zeno-like localization.

Contribution

It introduces the concept of Zeno-localization caused by small bath coupling and demonstrates the non-monotonic effect of bath coupling on localization through numerical analysis.

Findings

Weak bath coupling facilitates transport by energy borrowing.

Strong coupling leads to Zeno-localization due to orthogonality catastrophe.

The effect of bath coupling on localization is non-monotonic.

Abstract

We investigate what happens if an Anderson localized system is coupled to a small bath, with a discrete spectrum, when the coupling between system and bath is specially chosen so as to never localize the bath. We find that the effect of the bath on localization in the system is a non-monotonic function of the coupling between system and bath. At weak couplings, the bath facilitates transport by allowing the system to 'borrow' energy from the bath. But above a certain coupling the bath produces localization, because of an orthogonality catastrophe, whereby the bath 'dresses' the system and hence suppresses the hopping matrix element. We call this last regime the regime of "Zeno-localization", since the physics of this regime is akin to the quantum Zeno effect, where frequent measurements of the position of a particle impede its motion. We confirm our results by numerical exact diagonalization.