Parametric amplification of topological interface states in synthetic Andreev bands

TL;DR

This paper theoretically explores how nonlinear, driven-dissipative photonic systems can host topological interface states in synthetic bands, which can be amplified through parametric processes, revealing new topological phenomena in bosonic systems.

Contribution

It introduces the concept of parametric amplification of topological interface states in synthetic Andreev bands within nonlinear photonic systems.

Findings

Existence of Andreev-like bound states in a superfluid-normal-superfluid structure.

Formation of topological synthetic bands dependent on phase difference.

Nonlinear coupling leads to self-amplified topological states.

Abstract

A driven-dissipative nonlinear photonic system (e.g. exciton-polaritons) can operate in a gapped superfluid regime. We theoretically demonstrate that the reflection of a linear wave on this superfluid is an analogue of the Andreev reflection of an electron on a superconductor. A normal region surrounded by two superfluids is found to host Andreev-like bound states. These bound states form topological synthetic bands versus the phase difference between the two superfluids. Changing the width of the normal region allows to invert the band topology and to create "interface" states. Instead of demonstrating a linear crossing, synthetic bands are attracted by the non-linear non-Hermitian coupling of bosonic systems which gives rise to a self-amplified strongly occupied topological state.