Shanghai Institute Of Optics And Precision Machinery And Others Make Progress in The Study Of Bose-Einstein Condensation Of Synergistic Exciton Polarized Excitons

Recently, the team of Hongxing Dong and Long Zhang, researchers from the Infrared Optical Materials Research Center, Department of Advanced Laser and Optoelectronic Functional Materials, Shanghai Institute of Optics and Precision Machinery, Chinese Academy of Sciences (SIPM), together with the researchers from East China Normal University, have resolved the kinetic process and physical mechanism of the phase transition from hyperfluorescence to coexciton polarized exciton condensation based on the thin film system of chalcogenide quantum dots. The related research results, titled Observation of Transition from Superfluorescence to Polariton Condensation in CsPbBr3 Quantum Dots Film, were published in Light: Science & Applications (Light -Light: Science & Applications.
Hyperfluorescence is an ideal platform for studying many-body correlation mechanisms in exciton systems as well as developing bright quantum light sources and ultrafast optics. Meanwhile, coexcitons are characterized by higher vibronic strength, which is conducive to the study of the nonlinear nature of coexcitons, and it is easier to realize the coexciton polarized exciton condensation, which is helpful to realize the applications in the fields of quantum logic gates, topological state excitations, and so on. At present, there are few studies on the regulation of the coupling strength between light and cooperative matter states and the phase transition mechanism from hyperfluorescence to coexciton polarized exciton condensation. Realization of light-cooperative matter state coupling strength tuning based on the quantum dot system and resolving the ultrafast phase transition regulated by the cavity optical field are crucial for the further development and application of quantum devices.
This study proposes the introduction of an external cavity to tune the coupling strength between light and cooperative excitons, based on the structure of chalcogenide quantum dots thin films on the half-cavity of a distributed Bragg reflector demonstrates the strong coupling phenomenon between cooperative excitons and Bragg modes with a Rabi splitting of 21.6 meV. Further, the study observes the phenomenon of coalescence of polarized excitons of cooperative excitons. It is found that the involved correlated excitons exhibit significant coupling enhancement. This is mainly due to the random phase synchronization caused by the synergistic effect induced excitons, which results in the formation of macroscopic dipole moments with consistent polarization directions. The new quasiparticle Bose-Einstein condensation provides new possibilities for the development of ultra-narrow tunable lasers. In addition, the two-optical-matter properties of the synergistic exciton polarized exciton condensation expand its potential applications in quantum simulations, unconventional coherent light sources, and all-optical polarization logic devices.
The research work is supported by the National Natural Science Foundation of China, Shanghai Young Top Talent Program and Shanghai Leading Talent Training Program.