Circularly Polarized Luminescence Without External Magnetic Fields from Individual CsPbBr3 Perovskite Quantum Dots
arxiv(2024)
摘要
Lead halide perovskite quantum dots (QDs), the latest generation of colloidal
QD family, exhibit outstanding optical properties which are now exploited as
both classical and quantum light sources. Most of their rather exceptional
properties are related to the peculiar exciton fine-structure of band-edge
states which can support unique bright triplet excitons. The degeneracy of the
bright triplet excitons is lifted with energetic splitting in the order of
millielectronvolts, which can be resolved by the photoluminescence (PL)
measurements of single QDs at cryogenic temperatures. Each bright exciton
fine-structure-state (FSS) exhibits a dominantly linear polarization, in line
with several theoretical models based on the sole crystal field, exchange
interaction and shape anisotropy. Here, we show that in addition to a high
degree of linear polarization, the individual exciton FSS can exhibit a
non-negligible degree of circular polarization even without external magnetic
fields by investigating the four Stokes parameters of the exciton
fine-structure in individual CsPbBr3 QDs through Stokes polarimetric
measurements. We observe a degree of circular polarization up to 38
could not be detected by using the conventional polarimetric technique. In
addition, we found a consistent transition from left- to right-hand circular
polarization within the fine-structure triplet manifold, which was observed in
magnetic field dependent experiments. Our optical investigation provides deeper
insights into the nature of the exciton fine-structures and thereby drives the
yet-incomplete understanding of the unique photophysical properties of this
novel class of QDs, potentially opening new scenarios in chiral quantum optics.
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