Emergent Weyl excitations in systems of polar particles

TL;DR

This paper demonstrates that Weyl excitations can naturally occur in three-dimensional dipolar particle systems with broken time-reversal symmetry, offering a new platform for exploring Weyl physics in atomic systems.

Contribution

It shows that Weyl quasiparticles emerge in dipolar systems with weakly broken time-reversal symmetry, providing a feasible route for experimental realization in cold atomic setups.

Findings

Weyl excitations exist in 3D dipolar particle systems.

Angular momentum transfer induces Weyl dispersion.

Proposes momentum-resolved Ramsey spectroscopy for detection.

Abstract

Weyl fermions are massless chiral particles first predicted in 1929 and once thought to describe neutrinos. Although never observed as elementary particles, quasiparticles with Weyl dispersion have recently been experimentally discovered in solid-state systems causing a furore in the research community. Systems with Weyl excitations can display a plethora of fascinating phenomena and offer great potential for improved quantum technologies. Here we show that Weyl excitations generically exist in three-dimensional systems of dipolar particles with weakly broken time-reversal symmetry (for example, by a magnetic field). They emerge as a result of dipolar-interaction-induced transfer of angular momentum between the $J=0$ and $J=1$ internal particle levels. We also discuss momentum-resolved Ramsey spectroscopy methods for observing Weyl quasiparticles in cold alkaline-earth-atom systems. Our results provide a pathway for a feasible experimental realisation of Weyl quasiparticles and related phenomena in clean and controllable atomic systems.