Loss/gain-induced Hall effect of vortex light
Phys. Rev. B 113, 245309 – Published 25 June, 2026
DOI: https://doi.org/10.1103/kbtk-sy51
Abstract
The Hall effect provides a route for unidirectional manipulations of classical and quantum waves. In optics, the spin Hall effect (SHE) induced by the interaction between intrinsic angular momentum (AM) and material inhomogeneity enables AM-dependent control of light at the subwavelength scale. Despite its significance across various bulk and nanostructured geometries, the effect of non-Hermiticity on the optical Hall effect is generally assumed to be trivial except at the exceptional points in parity-time symmetric systems with tailored gain and loss. Here, we demonstrate the nontrivial Hall effect for light carrying both spin and orbital AM in a general non-Hermitian medium by revealing the emergent Hall shifts which rely solely on loss/gain of the systems. We demonstrate that loss or gain at a simple sharp interface introduce a spectral-selective absorption of light through a complex-valued geometrical phase, leading to AM-related corrections to the usual transverse SHE, including the transverse momentum shift, and the spin-orbit and nonlinear orbital Hall shifts along the longitudinal direction. We also propose to engineer and enhance the Hall effect with non-Hermitian gradient metasurfaces. We generalize the analysis to the propagation of light in inhomogeneous continuous media in the framework of geometrodynamics and identify the anomalous velocities due to non-Hermiticity as the counterparts of the interfacial Hall effect. Our work not only deepens our understanding of the Hall effect but also enables subwavelength light manipulations in non-Hermitian optical systems.
