Zero-field quantum beats and spin decoherence mechanisms in CsPbBr3 perovskite nanocrystals

Abstract

Coherent optical manipulation of exciton states provides a fascinating approach for quantum gating and ultrafast switching. However, their coherence time for incumbent semiconductors is highly susceptible to thermal decoherence and inhomogeneous broadening effects. Here, we uncover zero-field exciton quantum beating and anomalous temperature dependence of the exciton spin lifetimes in CsPbBr3 perovskite nanocrystals (NCs) ensembles. The quantum beating between two exciton fine-structure splitting (FSS) levels enables coherent ultrafast optical control of the excitonic degree of freedom. From the anomalous temperature dependence, we identify and fully parametrize all the regimes of exciton spin depolarization, finding that approaching room temperature, it is dominated by a motional narrowing process governed by the exciton multilevel coherence. Importantly, our results present an unambiguous full physical picture of the complex interplay of the underlying spin decoherence mechanisms. These intrinsic exciton FSS states in perovskite NCs present fresh opportunities for spin-based photonic quantum technologies.

Electron Spin Decoherence Dynamics in Magnetic Manganese Hybrid Organic–Inorganic Crystals: The Effect of Lattice Dimensionality

“…Although the spin decoherence dynamics has been extensively probed in metal hybrid materials employing ultrafast transient optical techniques, it is mainly centered on lead- or tin-based hybrids, which are nonmagnetic and often show extremely short spin relaxation lifetimes (mostly at the scale of a few , or tens of picoseconds , ) even at cryogenic temperatures. Most studies reveal that the τ 2 decays with the temperature because of the strong coupling of electron and phonon scattering; however, some recent reports demonstrate that an elevated temperature may increase τ 2 owing to motional narrowing . The different temperature dependence may be associated with the lattice dimensionality, metallic elements, or vibrational modes of metal hybrids and requires a more in-depth spin decoherence investigation.…”

Sub-Single-Exciton Optical Gain in Lead Halide Perovskite Quantum Dots Revealed by Exciton Polarization Spectroscopy

“…Moreover, in realistic samples, a complex interplay among Δ s , E b , and γ leads to spectral congestion of SE, XB, and XXA, strongly complicating their assignments. To resolve these issues, here we implement polarization-resolved TA ,− to study low-threshold optical gain from perovskite QDs. The polarizations of the pump and probe pulses are controlled to be either circular or linear through combinations of polarizers and waveplates, as depicted in Figure b.…”

“…5 ps (insets in Figure b,d), which is also the time scale for the decay of SE on the σ + σ + -spectra and XXA on the σ + σ – spectra (Figure S4). This time scale corresponds to the exciton spin depolarization/dephasing process, ,, after which all polarization schemes give identical TA spectra. In principle, after reaching full-spin randomization, the SE features should decay to half of their maximum amplitudes at an early time.…”

Nanoscale 0D/1D Heterojunction of MAPbBr3/COF Toward Efficient LED-Driven S–S Coupling Reactions

“…Furthermore, benefiting from the high photon quantum efficiency jointly enhanced by the size-induced quantum confinement effect and the corresponding energy band/level splitting on zero-dimensional (0D) quantum dots (QDs), MAPB QDs exhibit promising applications in photocatalystrelated fields. 43,44 In particular, QD photocatalysts for organic reactions are still in their infancy. However, the negative carrier recombination proportion and high photoluminescence efficiency with a slight Stokes shift make them unfavorable as photocatalysts for organic reactions.…”

“…The B-site is typically occupied by the metal cation from main groups IVA and VA (Pb 2+ and Bi 3+ ), meanwhile the X-site is selected from group VIIA (Cl – , Br – , and I – ). − The well-matched direct band gap to solar spectrum and excellent separation efficiency of carriers make MAPbBr 3 (MAPB) superior to other candidates, and significant advancements have been achieved in the fields of light-emitting diodes, solar cells, and photocatalysts, among others. Furthermore, benefiting from the high photon quantum efficiency jointly enhanced by the size-induced quantum confinement effect and the corresponding energy band/level splitting on zero-dimensional (0D) quantum dots (QDs), MAPB QDs exhibit promising applications in photocatalyst-related fields. , In particular, QD photocatalysts for organic reactions are still in their infancy. However, the negative carrier recombination proportion and high photoluminescence efficiency with a slight Stokes shift make them unfavorable as photocatalysts for organic reactions.…”