Spinor Slow-Light and Dirac particles with variable mass

TL;DR

This paper demonstrates how to create and control spinor slow-light polaritons with variable mass in an atomic ensemble, enabling simulation of Dirac particles and phenomena like localized zero-energy states.

Contribution

It introduces a method to realize Dirac-like spectra and variable mass for light-matter quasi-particles using a tripod atomic scheme with controllable two-photon detuning.

Findings

Realization of Dirac-like spectrum for slow-light polaritons.

Ability to induce and control mass, including sign reversal.

Potential to simulate the random-mass Dirac model with localized states.

Abstract

We consider the interaction of two weak probe fields of light with an atomic ensemble coherently driven by two pairs of standing wave laser fields in a tripod-type linkage scheme. The system is shown to exhibit a Dirac-like spectrum for light-matter quasi-particles with multiple dark-states, termed spinor slow-light polaritons (SSP). They posses an "effective speed of light" given by the group-velocity of slow-light, and can be made massive by inducing a small two-photon detuning. Control of the two-photon detuning can be used to locally vary the mass including a sign flip. This allows e.g. the implementation of the random-mass Dirac model for which localized zero-energy (mid-gap) states exist with unsual long-range correlations.