Ultrafast phonon-mediated dephasing of color centers in hexagonal boron nitride probed by electron beams
arxiv(2024)
摘要
Defect centers in hexagonal boron nitride have been extensively studied as
room temperature single photon sources. The electronic structure of these
defects exhibits strong coupling to phonons, as evidenced by the observation of
phonon sidebands in both photoluminescence and cathodoluminescence spectra.
However, the dynamics of the electron phonon coupling as well as phonon
mediated dephasing of the color centers in hexagonal boron nitride remain
unexplored. Here, we apply a novel time resolved CL spectroscopy technique to
explore the population decay to phonon states and the dephasing time T2 with
sub femtosecond time resolution. We demonstrate an ultrafast dephasing time of
only 200 fs and a radiative decay of about 585 fs at room temperature, in
contrast with all optical time resolved photoluminescence techniques that
report a decay of a few nanoseconds. This behavior is attributed to efficient
electron-beam excitation of coherent phonon polaritons in hexagonal boron
nitride, resulting in faster dephasing of electronic transitions. Our results
demonstrate the capability of our sequential cathodoluminescence spectroscopy
technique to probe the ultrafast dephasing time of single emitters in quantum
materials with sub femtosecond time resolution, heralding access to quantum
path interferences in single emitters coupled to their complex environment.
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