Topologically tunable polaritons based on two-dimensional crystals in a photonic lattice

TL;DR

This paper demonstrates tunable topological polaritons in a 2D material-based photonic lattice at room temperature, enabling control over topological states and their spectral properties for advanced photonic applications.

Contribution

It introduces a novel platform using WS2 monolayers in an optical cavity to realize and manipulate topological polariton states emulating the SSH Hamiltonian.

Findings

Achieved spectral tunability of topological polariton modes over 80 meV.

Demonstrated transformation of the SSH lattice into a Stark-ladder, coupling topological modes to propagating states.

Quantified the Zak-phase difference between topological phases as approximately 1.13π.

Abstract

Topological photonics is an emergent research discipline which interlinks fundamental aspects of photonics, information processing and solid-state physics. Exciton-polaritons are a specifically interesting platform to study topological phenomena, since the coherent light matter coupling enables new degrees of freedom such as tunable non-linearities, chiralities and dissipation. Room-temperature operation of such exciton-polaritons relies on materials comprising both, large exciton binding energies and oscillator strength. We harness widely spectrally tunable, room temperature exciton-polaritons based on a WS2 monolayer in an open optical cavity to realize a polariton potential landscape which emulates the Su-Schrieffer-Heeger (SSH) Hamiltonian. It comprises a domain boundary hosting a topological, exponentially localized mode at the interface between two lattices characterized by different Zak-phases which features a spectral tunability over a range as large as 80 meV. Moreover, we utilize the unique tilt-tunability of our implementation, to transform the SSH-lattice into a Stark-ladder. This transformation couples the topologically protected defect mode to propagating lattice modes, and effectively changes the symmetry of the system. Furthermore, it allows us to directly quantify the Zak-phase difference $\Delta_{Zak}=(1.13\pm 0.11)\pi$ between the two topological phases. Our work comprises an important step towards in-situ tuning topological lattices to control and guide light on non-linear chips.