Chiral near-fields at achiral plasmonic tips enable nanoscale valley polarimetry

Abstract

Optical helicity is central to chiral light-matter interactions, yet plasmonic confinement typically distorts it at the nanoscale. Here, we demonstrate nanoscale valley polarimetry using an achiral Au tip, where incidence-angle control of circularly polarized light creates a strongly localized, helicity-preserving near-field. Chiral tip-enhanced photoluminescence (c-TEPL) directly resolves and reverses local valley polarization in monolayer WSe2 and reveals nanoscale polarization variations in strained MoS2 hidden by diffraction-limited measurements.