Fig. 4: Measurement of the exciton optical coherence lifetime.
From: The dark exciton ground state promotes photon-pair emission in individual perovskite nanocrystals
a Low-temperature PL spectrum of a NC presenting a single ZPL. The origin of the energy scale is taken at the ZPL. The low-energy part of the spectrum is magnified by a factor of 20. Six LO phonon modes are identified with phonon energies 3.0, 3.5, 5.4, ~8, ~11, ~15 meV. To record a resonant PL excitation spectrum, the frequency of a single-mode laser is scanned across a ZPL, while photons emitted on the highest phonon-energy LO phonon sidebands are collected through a low-pass filter (transmission curve illustrated by the red line). b Resonant PL spectrum built from a sum of 9 scans (1 s per scan, 1 ms per bin), with an excitation intensity of 20 W cm−2. It is fitted with a Lorentzian profile (red curve) with a FWHM linewidth of 5 GHz. c Typical PL decay of a single NC, for an average number of exciton per pulse 〈N〉 = 0.2. The red curve is an exponential fit with a lifetime of 1.0 ns. The instrument response function is shown in gray.
