Inhibition of tunnelling and edge state control in polariton topological insulators

TL;DR

This paper investigates how dynamical modulation of potential wells in polariton topological insulators can inhibit tunnelling and control edge state velocities, enabling slowing or stopping of edge states through resonance effects.

Contribution

It introduces a method to control edge state velocities in polariton topological insulators via weak out-of-phase potential modulations, revealing resonance-based tunnelling inhibition.

Findings

Edge states can be slowed down or halted using specific modulation frequencies.

Resonant frequencies cause significant changes in edge state dispersion.

Splitting of edge states occurs at frequencies above resonance.

Abstract

We address the inhibition of tunnelling in polariton condensates confined in a potential landscape created by a honeycomb array of microcavity pillars in the presence of spin-orbit coupling and Zeeman splitting in the external magnetic field. The coupling rate between the microcavity pillars can be strongly impacted even by weak out-of-phase temporal modulations of the depths of the corresponding potential wells. When such a modulation is implemented in truncated honeycomb arrays that realize a polariton topological insulator, which supports unidirectional edge states in the presence of spin-orbit coupling and Zeeman splitting, it allows controlling the velocity of the states. The origin of the phenomenon is the dynamical modulation with a proper frequency, which notably changes the dispersion of the system and the group velocity of edge states. We show that such a control is possible for modulation frequencies close to resonances for inhibition of tunnelling in a two-well configuration. Edge states considerably slow down, and even stop completely, when the modulation frequency approaches a resonant value, while above such frequency splitting of the edge states into wavepackets moving with different velocities occurs.