Colossal anomalous Stark shift in defect emission of undulated 2D materials

TL;DR

This paper discovers a colossal Stark shift in defect emissions of undulated 2D materials caused by mirror symmetry breaking, driven by flexo-dipole interactions, with potential applications in nano-electro-mechanical and photonic devices.

Contribution

It reveals a new anomalous Stark effect in 2D materials due to flexo-dipole coupling, exceeding traditional Stark shifts by orders of magnitude.

Findings

Zero-phonon line shifts >500 meV in bent 2D hBN defects

Shift magnitude depends on curvature and bending direction

Method to identify nanotube chirality and explain emitter variability

Abstract

We report a strikingly new physical phenomenon that mirror symmetry breaking in undulated two-dimensional (2D) materials induces a colossal Stark shift in defect emissions, occurring without external electric field F, termed anomalous Stark effect. First-principles calculations of multiple defects in bent 2D hBN uncover the fundamental physical reasonings for this anomalous effect and reveal this arises due to strong coupling between flexoelectric polarization and defect dipole moment. This flexo-dipole interaction, similar to that in traditional Stark effect due to F, results in zero-phonon line (ZPL) shifts >500 meV for defects like NBVN and CBVN at $\kappa$ = 1/nm, exceeding typical Stark shifts by 2-3 orders of magnitude. The large ZPL shifts variations with curvature and bending direction offers a method to identify nanotube chirality and explain the large variability in single photon emitters' wavelength in 2D materials, with additional implications for designing nano-electro-mechanical and photonic devices.