Stimulated emission depletion spectroscopy of color centers in hexagonal boron nitride

TL;DR

This paper uses Stimulated Emission Depletion spectroscopy to map the electron-optical-phonon sideband of color centers in hexagonal boron nitride, revealing a red-shift in phonon peaks and comparing it with photoluminescence excitation spectra.

Contribution

It demonstrates the application of STED spectroscopy to analyze the phonon sidebands of color centers in hBN, providing new insights into their electronic and vibrational structure.

Findings

Red-shift observed in the longitudinal optical phonon peak.

Comparison shows qualitative differences between STED and PLE spectra.

Results suggest admixture of excited states in the defect structure.

Abstract

We demonstrate the use of Stimulated Emission Depletion (STED) spectroscopy to map the electron-optical-phonon sideband of the ground state of the radiative transition of color centers in hexagonal boron nitride emitting at 2.0-2.2 eV, with in-plane linear polarization. The measurements are compared to Photoluminescence of Excitation (PLE) spectra, that maps the electron-optical-phonon sideband of the excited state. The main qualitative difference is a red-shift in the longitudinal optical phonon peak associated with $E_{1u}$ symmetry at the zone center. We argue that this is consistent with recent findings for a carbon-based line defect with admixture of energetically similar excited states.