Temperature Dependence of Wavelength Selectable Zero-Phonon Emission from Single Defects in Hexagonal Boron Nitride

TL;DR

This study explores the temperature-dependent optical properties of zero-phonon emission from defect-based single photon sources in hexagonal boron nitride, revealing insights into their spectral behavior and excitation mechanisms.

Contribution

It provides a detailed analysis of temperature effects on zero-phonon lines in h-BN and introduces a lattice vibration model considering piezoelectric coupling for understanding these properties.

Findings

Zero-phonon emission lines are distributed over a 500 meV energy range.

Temperature dependence of linewidth and spectral shift is similar for different emission lines.

Polarization measurements suggest different excitation pathways for the two lines.

Abstract

We investigate the distribution and temperature-dependent optical properties of sharp, zero-phonon emission from defect-based single photon sources in multilayer hexagonal boron nitride (h-BN) flakes. We observe sharp emission lines from optically active defects distributed across an energy range that exceeds 500 meV. Spectrally-resolved photon-correlation measurements verify single photon emission, even when multiple emission lines are simultaneously excited within the same h-BN flake. We also present a detailed study of the temperature-dependent linewidth, spectral energy shift, and intensity for two different zero-phonon lines centered at 575 nm and 682 nm, which reveals a nearly identical temperature dependence despite a large difference in transition energy. Our temperature-dependent results are best described by a lattice vibration model that considers piezoelectric coupling to in-plane phonons. Finally, polarization spectroscopy measurements suggest that whereas the 575 nm emission line is directly excited by 532 nm excitation, the 682 nm line is excited indirectly.