Zhaoyang Zhang, Ismaël Septembre, Zhenzhi Liu, Pavel Kokhanchik, Shun Liang, Fu Liu, Changbiao Li, Hongxing Wang, Maochang Liu, Yanpeng Zhang, Min Xiao, Guillaume Malpuech, Dmitry Solnyshkov
Exceptional rings are sets of non-Hermitian singularities stemming from Dirac points. We study them theoretically and experimentally in an atomic vapor cell. We demonstrate the formation of an exceptional ring in a photonic honeycomb lattice by showing a transition between conical diffraction and non-Hermitian broadening of a beam in real space. We further predict and demonstrate an original non-Hermitian effect: the transverse non-Hermitian drift. It is similar to the anomalous Hall effect, but it occurs in reciprocal space, and its description requires a biorthogonal quantum metric. The non-Hermitian drift can be used for applications in beam steering.