Coupling to Octahedral Tilts in Halide-Perovskite Nanocrystals Induces Phonon-Mediated Attractive Interactions between Excitons
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2023-08-10Type
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Abstract
Understanding the origin of electron-phonon coupling in lead-halide perovskites
is key to interpreting and leveraging their optical and electronic properties. Here,
we show that photoexcitation drives a reduction of the lead-halide-lead bond
angles, a result of deformation potential coupling to low energy optical phonons.
We accomplish this by performing femtosecond-resolved, optical-pump, electrondiffraction-
probe measurements to quantify the lattice reorganization occurring
as a result of photoexcitation in nanocrystals of FAPbBr3 and CsPbBr3. Our
results indicate a stronger coupling in FAPbBr3 compared to CsPbBr3. We
attribute the enhanced coupling in FAPbBr3 to its disordered crystal structure,
which persists down to cryogenic temperatures. We find the reorganizations
induced by each exciton in a multi-excitonic state constructively interfere, giving
rise to a coupling strength which scales quadratically with the exciton number.
This super-linear scaling induces phonon-mediated attractive interactions
between excitations in lead-halide perovskites. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000626244Publisher
ETH ZurichOrganisational unit
03895 - Wood, Vanessa / Wood, Vanessa
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