Valley-dependent wavepacket self-rotation and Zitterbewegung in symmetry-broken honeycomb lattices

TL;DR

This paper demonstrates valley-dependent wavepacket self-rotation and Zitterbewegung in symmetry-broken honeycomb photonic lattices, revealing topological effects and valley-specific dynamics without initial orbital angular momentum.

Contribution

It introduces a novel valley-dependent self-rotation phenomenon in photonic lattices driven by Berry phase effects, expanding understanding of topological wave dynamics.

Findings

Wavepacket self-rotation manifests as spiraling intensity patterns.

Self-rotation is induced by Berry phase and results in Zitterbewegung oscillations.

The oscillation frequency depends on the bandgap and is valley-dependent.

Abstract

The toolbox quantities used for manipulating the flow of light include typically amplitude, phase, and polarization. Pseudospins, such as those arising from valley degrees of freedom in photonic structures, have recently emerged as an excellent candidate for this toolbox, in parallel with rapid development of spintronics and valleytronics in condensed-matter physics. Here, by employing symmetry-broken honeycomb photonic lattices, we demonstrate valley-dependent wavepacket self-rotation manifested in spiraling intensity patterns, which occurs without any initial orbital angular momentum. Theoretically, we show that such wavepacket self-rotation is induced by the Berry phase and results in Zitterbewegung oscillations. The "center-of-mass" of the wavepacket oscillates at a gap-dependent frequency, while the helicity of self-rotation is valley-dependent, that is, correlated with the Berry curvature. Our results lead to new understanding of the venerable Zitterbewegung phenomenon from the perspective of topology and are readily applicable on other platforms such as two-dimensional Dirac materials and ultracold atoms.