Electronic transitions of single silicon vacancy centers in the near-infrared spectral region

TL;DR

This study demonstrates that the near-infrared photoluminescence lines in single silicon vacancy centers are due to an additional electronic transition, confirmed through polarization and correlation measurements, revealing fast switching between transitions.

Contribution

It provides direct experimental evidence that NIR PL lines in SiV centers are due to a separate electronic transition, not vibronic or metastable states, with detailed polarization and correlation analysis.

Findings

NIR line at 822.7 nm has a linewidth of 1.4 nm at room temperature.

NIR and ZPL lines originate from the same SiV center with anti-correlated emission.

Fast switching between transitions occurs with a characteristic time of 0.7 ns.

Abstract

Photoluminescence (PL) spectra of single silicon vacancy (SiV) centers frequently feature very narrow room temperature PL lines in the near-infrared (NIR) spectral region, mostly between 820 nm and 840 nm, in addition to the well known zero-phonon-line (ZPL) at approx. 738 nm [E. Neu et al., Phys. Rev. B 84, 205211 (2011)]. We here exemplarily prove for a single SiV center that this NIR PL is due to an additional purely electronic transition (ZPL). For the NIR line at 822.7 nm, we find a room temperature linewidth of 1.4 nm (2.6 meV). The line saturates at similar excitation power as the ZPL. ZPL and NIR line exhibit identical polarization properties. Cross-correlation measurements between the ZPL and the NIR line reveal anti-correlated emission and prove that the lines originate from a single SiV center, furthermore indicating a fast switching between the transitions (0.7 ns). g(2) auto-correlation measurements exclude that the NIR line is a vibronic sideband or that it arises due to a transition from/to a meta-stable (shelving) state.