The effect of electron-phonon interactions on the spectral properties of single defects in hexagonal boron nitride

TL;DR

This study explores how electron-phonon interactions influence the spectral features of a single defect in hexagonal boron nitride, revealing temperature-dependent behaviors and phonon sidebands through experimental and theoretical analysis.

Contribution

It introduces a quadratic electron-phonon interaction model to explain temperature effects on spectral lineshape and linewidth of defect emission in hBN.

Findings

ZPL linewidth at 78 K is 172 μeV.

Spectral lineshape follows T+T^5 broadening and T+T^3 shift.

Debye-Waller factor of ZPL emission is 0.59.

Abstract

We investigate temperature-dependent spectral properties of a single defect in hexagonal boron nitride (hBN). We observe a sharp zero-phonon line (ZPL) emission accompanied by Stokes and anti-Stokes optical phonon sidebands assisted by the Raman active low-energy ($\approx~6.5$ meV) interlayer shear mode of hBN. Spectral lineshape around the ZPL is measured down to 78 K, at which the linewidth of the ZPL is measured as 172 $\mu$eV. By employing a quadratic electron-phonon interaction, the temperature-dependent broadening and the lineshift of the ZPL are found to follow $T+T^5$ and $T+T^3$ temperature dependence, respectively. Furthermore, the temperature-dependent lineshape around the ZPL is modeled with a linear electron-phonon coupling theory, which results in the Debye-Waller factor of the ZPL emission as 0.59.