Light Emission from Single Perovskite Quantum Dots

Lead halide perovskite nanocrystals are of broad interest as classical light sources (LED/LCD displays) and as quantum light sources (quantum sensing and imaging, quantum communication, optical quantum computing). Studies at the single-particle level unravel the pure photophysics of these novel quantum dots. Most of the rather exceptional properties are related to the peculiar exciton fine-structure of band-edge states, with emission through bright triplet excitons at low temperatures. Perovskite QDs exhibit giant oscillator strength phenomena and single-photon emission, making them the fastest single-photon colloidal QD emitters [1]. The nondegenerate bright triplet excitons, with millielectronvolts-scale splitting, exhibit predominantly linear polarization, as anticipated theoretically accounting for the crystal field, exchange interaction, and shape anisotropy. However, one also sees 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 [2]. A degree of circular polarization up to ~38% is determined, which could not be detected by using the conventional polarimetric technique. The ultimate goal of quantum optics is to achieve exquisite control of light-matter interaction at the single-quanta level. Chiral photons are particularly advantageous because they carry background-free binary data, and the spin-controlled light propagation direction promises powerful nonreciprocal quantum devices. We also present the generation of strongly chiral emission in single perovskite QDs by placing them near chiral plasmonic particles, boosting the degree of circular polarization by an order of magnitude. The chirality transfer occurs through the interaction of the local chiral plasmonic field with the photonic states of the perovskite NCs. The handedness anisotropy of both excitation and emission showed an order of magnitude increase at the presence of chiral field, which was accompanied by a 3-4-fold acceleration of the radiative decay rate.<br/><br/>[1] C. Zhu, S.C. Boehme, L.G. Feld, A. Moskalenko, D.N. Dirin, R.F. Mahrt, T. Stöferle, M.I. Bodnarchuk, A.L. Efros, P.C. Sercel, M.V. Kovalenko, G. Rainò.<br/>Nature, <b>2024</b>, 626, 535–541<br/>[2] V. Oddi, C. Zhu, M.A. Becker, Y. Sahin, D.N. Dirin, T. Kim, R.F. Mahrt, J. Even, G. Rainò, M.V. Kovalenko, T. Stöferle<br/>ACS Nano, <b>2024</b>, https://doi.org/10.1021/acsnano.4c04392<br/>[3] T.Kim, M.Svyrydenko, R. M. Kim, J. H. Han, K. T. Nam, M. Bodnarchuk, G.Raino, M. V. Kovalenko et al. in preparation