Plasmonic nanocavity-enabled universal detection of layer-breathing vibrations in two-dimensional materials

TL;DR

This paper introduces a plasmonic nanocavity-enhanced Raman spectroscopy method that universally detects interlayer vibrations in 2D materials, overcoming traditional limitations and providing a quantitative understanding of interlayer interactions.

Contribution

The study develops a plasmon-enhanced Raman technique and a polarizability model to detect and analyze layer-breathing modes in various 2D materials, including heterostructures.

Findings

Enhanced detection of LB modes in multilayer graphene and hBN.

Modified polarization selection rules due to plasmonic effects.

Quantitative model explaining intensity profiles and interfacial polarizability.

Abstract

Conventional Raman spectroscopy faces inherent limitations in detecting interlayer layer breathing (LB) vibrations with inherently weak electron-phonon coupling or Raman inactivity in two-dimensional materials, hindering insights into interfacial coupling and stacking dynamics. Here we demonstrate a universal plasmon-enhanced Raman spectroscopy strategy using gold or silver nanocavities to strongly enhance and detect LB modes in multilayer graphene, hBN, and their van der Waals heterostructures. Plasmonic nanocavities even modify the linear and circular polarization selection rules of the LB vibrations. By developing an electric-field-modulated interlayer bond polarizability model, we quantitatively explain the observed intensity profiles and reveal the synergistic roles of localized plasmonic field enhancement and interfacial polarizability modulation. This model successfully describes the behavior across different material systems and nanocavity geometries. This work not only overcomes traditional detection barriers but also provides a quantitative framework for probing interlayer interactions, offering a versatile platform for investigating hidden interfacial phonons and advancing the characterization of layered quantum materials.