Symmetry-protected photonic chiral spin textures by spin-orbit coupling

TL;DR

This paper presents a theoretical framework explaining how photonic chiral spin textures arise from symmetry and relativity principles at optical interfaces, linking their formation to conservation laws and energy transport.

Contribution

It introduces a variational theorem-based approach to understand the formation of photonic chiral spin textures from symmetry considerations, bridging condensed matter and optical systems.

Findings

Photonic chiral spin textures are derived from symmetry and relativity principles.

Conservation of total angular momentum influences local spin vector twisting.

The framework links photonic and condensed-matter chiral spin textures mechanisms.

Abstract

Chiral spin textures are researched widely in condensed matter systems and show potential for spintronics and storage applications. Along with extensive condensed-matter studies of chiral spin textures, photonic counterparts of these textures have been observed in various optical systems with broken inversion symmetry. Unfortunately, the resemblances are only phenomenological. This work proposes a theoretical framework based on the variational theorem to show that the formation of photonic chiral spin textures in an optical interface is derived from the system's symmetry and relativity. Analysis of the optical system's rotational symmetry indicates that conservation of the total angular momentum is preserved from the local variations of spin vectors. Specifically, although the integral spin momentum does not carry net energy, the local spin momentum distribution, which determines the local subluminal energy transport and minimization variation of the square of total angular momentum, results in the chiral twisting of the spin vectors. The findings here deepen the understanding of the symmetries, conservative laws and energy transportation in optical system, construct the comparability in the formation mechanisms and geometries of photonic and condensed-matter chiral spin textures, and suggest applications to optical manipulation and chiral photonics.