Optical access of spin-polarized excited states in Cs(PbMgZnCd)Br3 nanocrystals

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Original abstract

The interplay of slow spin relaxation (long τS) and fast radiative recombination (short τR) is essential for using spin-polarized excited states in lead halide perovskites towards spintronics and quantum-optics technologies. Herein, we report on the observation of simultaneously long τS (59.8 ps) and short τR (3.4 ns) in the colloidal nanocrystals of high-entropy perovskites, Cs(PbMgZnCd)Br3, which enables the optical access and spin manipulation of excited states at room temperature. The incorporation of non-Pb metals spatially separates the [PbBr6]4− framework into smaller domains below the Bohr radius of excitons, and the size confinement leads to blue-shifted bright photoluminescence from short-lived photoexcitation species. Moreover, the distortion of [PbBr6]4− lattice is significantly enhanced in high-entropy structures, which enlarges the Rashba spin splitting and consequently prolongs τS over an order of magnitude. Optical write-in and read-out of spin states via circularly polarized light are achieved for both photoluminescence and amplified spontaneous emission from Cs(PbMgZnCd)Br3. Optical Hanle effect is demonstrated and allows for very efficient spin manipulation (positive/negative polarizations ~25.8%) under a perpendicular magnetic field, showing the great potential of high-entropy perovskites for opto-spintronic applications. High-entropy perovskite nanocrystals prepared via ion exchange show a prolonged spin relaxation lifetime due to Rashba effect, which enables the manipulation of optically accessible spin-polarized excited states at room temperature.

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