@article{21548,
  abstract     = {Non-Abelian gauge fields provide a conceptual framework to describe particles
having spins, underlying many phenomena in electrodynamics, condensed-matter
physics and particle physics. Lattice models of non-Abelian gauge fields allow us
to understand their physical implications in extended systems. The theoretical
importance of non-Abelian lattice gauge fields motivates their experimental synthesis
and explorations. Photons are fundamental particles for which artificial gauge fields
can be synthesized, yet the demonstration of non-Abelian lattice gauge fields for
photons has not been achieved. Here we demonstrate SU(2) lattice gauge fields for
photons in the synthetic frequency dimensions, a playground to study lattice
physics in a scalable and programmable way. In our lattice model, we theoretically
observe that homogeneous non-Abelian lattice gauge potentials induce Dirac cones
at time-reversal-invariant momenta in the Brillouin zone. We experimentally confirm
the presence of non-Abelian lattice gauge fields by two signatures: linear band
crossings at the Dirac cones, and the associated direction reversal of eigenstate
trajectories. We further demonstrate a non-Abelian scalar lattice gauge potential that
lifts the degeneracies of the Dirac cones. Our results highlight the implications of
non-Abelian lattice gauge fields in topological physics, and provide a starting point
for demonstrations of emerging non-Abelian physics in the photonic synthetic
dimensions. Our results may also benefit photonic technologies by providing controls
of photon spins and pseudo-spins in topologically non-trivial ways.},
  author       = {Cheng, Dali and Wang, Kai and Roques-Carmes, Charles and Lustig, Eran and Long, Olivia Y. and Wang, Heming and Fan, Shanhui},
  issn         = {1476-4687},
  journal      = {Nature},
  number       = {8044},
  pages        = {52--56},
  publisher    = {Springer Nature},
  title        = {{Non-Abelian lattice gauge fields in photonic synthetic frequency dimensions}},
  doi          = {10.1038/s41586-024-08259-2},
  volume       = {637},
  year         = {2025},
}