Cut-offs and light-spin flips in surface plasmon resonance between a chiral medium and a metal

TL;DR

This paper derives a dispersion relation for surface plasmon resonance at a metal-chiral medium interface, revealing that chirality reduces phase speeds and affects energy distribution, with implications for spin-related phenomena.

Contribution

It introduces a new dispersion relation for surface plasmons on chiral media and compares it with the achiral case, highlighting unique effects of chirality.

Findings

Chiral media exhibit smaller phase speeds than achiral media.

Longitudinal spin density influences phase speed reduction.

Low-frequency surface plasmon modes are suppressed in chiral media.

Abstract

We have derived a dispersion relation governing the surface plasmon resonance established along a planar interface between a metal and a chiral medium (chiral case). Resulting numerical solutions are compared with the well-known results obtained for a metal-dielectric interface (achiral case). Comparisons show that the chiral case exhibits smaller phase speeds than the achiral case. Such a longitudinal deceleration in the chiral case is caused by the energy expended on establishing the longitudinal spin density, which turns out anti-symmetric with respect to medium chirality. Moreover, the low-frequency range is disallowed in the chiral case. Relevant energy redistributions, spin-orbital couplings, and applications are discussed.