Weyl singularities in polaritonic multi-terminal Josephson junctions

TL;DR

This paper theoretically explores Weyl singularities in multi-terminal polaritonic Josephson junctions, revealing topological Weyl points in a 4D parameter space and linking real-space vortices to band topology.

Contribution

It introduces a model for 5-terminal polaritonic Josephson junctions, identifying Weyl points and deriving an effective Hamiltonian for their dynamics in 4D parameter space.

Findings

Discovery of 4/6 Weyl points in 3D subspaces with different symmetries.

Linking real-space vortices to topological features in parameter space.

Derivation of an effective Hamiltonian for Weyl node dynamics.

Abstract

We study theoretically analog multi-terminal Josephson junctions formed by gapped superfluids created upon resonant pumping of cavity exciton-polaritons. We study the $p$-like bands of a 5-terminal junction in the 4D parameter space created by the superfluid phases acting as quasi-momenta. We find 4/6 Weyl points in 3D subspaces with preserved/broken time-reversal symmetry. We link the real space topology (vortices) to the parameter space one (Weyl points). We derive an effective Hamiltonian encoding the creation, motion, and annihilation of Weyl nodes in 4D. Our work paves the way to the study of exotic topological phases in a platform allowing direct measurement of eigenstates and band topology.