2021/08/02 by Peng Shi, Yang Aiping, Shi, Peng +9
Physics and Astronomy · #Atomic and Subatomic Physics Research #FOS: Physical sciences #Mechanical and Optical Resonators #Optics (physics.optics) #Topological Materials and Phenomena
paper · pdf · doi:10.48550/arxiv.2108.00725
openalex publication_date 2021/08/02 · openalex created_date 2022/07/25 · openalex updated_date 2026/07/28
Electromagnetic spins, including longitudinal and transverse ones, have been playing important roles in light-matter interactions. Here, we formulate a unified equation to uncover the physical origins and topological properties of longitudinal and transverse spins in a generic electromagnetic field. The equation reveals universally that the transverse spin is locked with the kinetic momentum and originated from the transverse inhomogeneities of field, whereas the helix-dependent longitudinal spin orients parallel to the local wavevector. Remarkably, a hidden extraordinary helix-dependent transverse spin possessing helix-dependent spin-momentum locking is discovered and the number of locking states consistent with the nontrivial topological spin Chern number. Furthermore, this spin which determines the inverted helical components is related to the Berry curvature closely. The findings, which are demonstrated experimentally by measuring the three-dimensional spin components in the focusing configuration, will deepen the understanding the underlying physics of spins and open an avenue for chiral quantum optical applications.