Self-interfering wavepackets

TL;DR

This paper explores how polariton wavepackets exhibit unique propagation behaviors due to dual mass concepts, leading to phenomena like wavepacket bouncing and the formation of spacetime crystals.

Contribution

It introduces a novel understanding of polariton wavepacket dynamics driven by dual mass effects and Rabi coupling, revealing new particle-like behaviors in non-interacting fields.

Findings

Polariton wavepackets can bounce on a 'mass wall' caused by diverging and sign-changing diffusive mass.

Rabi coupling shapes wavepackets into self-accelerating, particle-like objects.

Ultrafast subpackets and spacetime crystal ordering are observed in the propagation dynamics.

Abstract

We study the propagation of non-interacting polariton wavepackets. We show how two qualitatively different concepts of mass that arise from the peculiar polariton dispersion lead to a new type of particle-like object from non-interacting fields---much like self-accelerating beams---shaped by the Rabi coupling out of Gaussian initial states. A divergence and change of sign of the diffusive mass results in a "mass wall" on which polariton wavepackets bounce back. Together with the Rabi dynamics, this yield propagation of ultrafast subpackets and ordering of a spacetime crystal.