Interactions and scattering of quantum vortices in a polariton fluid

Lorenzo Dominici,Giuseppe Gigli,Jesús Cuevas-Maraver,Giovanni Lerario,Milena De Giorgi,Panayotis G Kevrekidis,Augusto S Rodrigues,Dimitri J Frantzeskakis,Ricardo Carretero-González,Antonio Gianfrate,Daniele Sanvitto,Dario Ballarini

doi:10.1038/s41467-018-03736-5

Abstract

Quantum vortices, the quantized version of classical vortices, play a prominent role in superfluid and superconductor phase transitions. However, their exploration at a particle level in open quantum systems has gained considerable attention only recently. Here we study vortex pair interactions in a resonant polariton fluid created in a solid-state microcavity. By tracking the vortices on picosecond time scales, we reveal the role of nonlinearity, as well as of density and phase gradients, in driving their rotational dynamics. Such effects are also responsible for the split of composite spin–vortex molecules into elementary half-vortices, when seeding opposite vorticity between the two spinorial components. Remarkably, we also observe that vortices placed in close proximity experience a pull–push scenario leading to unusual scattering-like events that can be described by a tunable effective potential. Understanding vortex interactions can be useful in quantum hydrodynamics and in the development of vortex-based lattices, gyroscopes, and logic devices.

Highlights

Quantum vortices, the quantized version of classical vortices, play a prominent role in superfluid and superconductor phase transitions
Polaritons support rich spinorial patterns, in analogy to optical systems and multicomponent BECs47,48. When considering both the spin and OAM degrees of freedom, three basic vortex configurations are most relevant: the full vortex (FV), that is composed of phase singularities with the same orbital charge in both spin populations; the spin vortex (SV), which, in contrast, is composed of opposite windings between the two spin components; and the half vortex (HV), that consists of a unit charge coupled to a chargeless configuration
The understanding and control of vortex–vortex interactions can play a role in quantum hydrodynamics[59], Bose–Einstein condensates (BECs) phase transitions[13], and pattern formation[60] or superfluid vacuum theories[31], as well as suggesting hints in the design of vortex lattices shaping[52], ultrasensitive gyroscopes[61], and information processing polariton devices[62]

Summary

Introduction

The quantized version of classical vortices, play a prominent role in superfluid and superconductor phase transitions. When the external pumping is increased— the total population and the effective nonlinearity—vortices are able to interact more strongly This increases the self-rotation effect and, in the case of a spinorial configuration with opposite-orbital charges between the two spin components, is able to split the spin–vortex states into their composing half-quantum vortices (i.e., baby-skyrmions[56]). The understanding and control of vortex–vortex interactions can play a role in quantum hydrodynamics[59], BECs phase transitions[13], and pattern formation[60] or superfluid vacuum theories[31], as well as suggesting hints in the design of vortex lattices shaping[52], ultrasensitive gyroscopes[61], and information processing polariton devices[62]

Methods

Results

Conclusion