Universal Scalings in Two-Dimensional Anisotropic Dipolar Excitonic Systems

Abstract

Low-dimensional excitonic materials have inspired much interest owing to their novel physical and technological prospects. In particular, those with strong in-plane anisotropy are among the most intriguing but short of general analyses. We establish the universal functional form of the anisotropic dispersion in the small k limit for 2D dipolar excitonic systems. While the energy is linearly dispersed in the direction parallel to the dipole in plane, the perpendicular direction is dispersionless up to linear order, which can be explained by the quantum interference effect of the interaction among the constituents of 1D subsystems. The anisotropic dispersion results in a E ∼0.5 scaling of the system density of states and predicts unique spectroscopic signatures including: (1) disorder-induced absorption linewidth, WðσÞ ∼ σ 2.8 , with σ the disorder strength, (2) temperature dependent absorption linewidth, WðTÞ ∼ T sþ1.5 , with s the exponent of the environment spectral density, and (3) the out-of-plane angular θ dependence of the peak splittings in absorption spectra, ΔEðθÞ ∝ sin 2 θ. These predictions are confirmed quantitatively with numerical simulations of molecular thin films and tubules.

Superradiance and Exciton Delocalization in Perovskite Quantum Dot Superlattices

“…The red-shifted and narrower PL emission for the SLs at low temperatures is an optical signature of superradiance, where the collective excitonic states are shared by more than one QD. The energy shift is proportional to the effective dipole coupling strength V. 28 As detailed in the Supporting Information, we estimated V to be ∼16 meV, which is on the same order as the observed PL peak shift at 11 K and an order of magnitude higher than CdSe QD SLs. 29 Temperature-dependent reflectance spectra further confirm that red-shifted PL emission originated from the delocalized superradiant state.…”

Coherent Spatial Control of Wave Packet Dynamics on Quantum Lattices

“…Our analysis of the traveling wave packet can also find its relevance in polariton transport in optical cavities. − While optical excitation spreads over many lattice spacings, often exceeding the critical width of w c , quantum technology platforms such as optical lattices , and superconducting circuits − can achieve local excitation and fine-tune the initial spreading and spatial modulation, rendering stringent experimental tests of our predictions. These new experiments motivate the extension of our study to disordered higher-dimensional lattices coupled to phonons. , …”

“…The rapid advancement in quantum materials and quantum information science has generated renewed interest in quantum lattices of two archetypes: molecular crystals and quantum engineering platforms. Molecular crystals encompass a broad range of organic and inorganic compounds and have demonstrated remarkable potential in charge − and excited state energy transport − in terms of tunability and cost-effectiveness. These materials, often characterized by their well-ordered structures, are ideal platforms for quantum coherent control studies.…”

Bridging the Gap between H- and J-Aggregates: Classification and Supramolecular Tunability for Excitonic Band Structures in 2-Dimensional Molecular Aggregates

“…34 For 2D excitonic systems with non-nearest neighbor dipoledipole couplings, the system DOS scaling has been shown to follow a 𝑑 = 0.5 dependence. 57 Thus, we obtain 𝑠 = 0 for TDBC and 𝑠 ~− 0.5 for the rest of the benzothiazole Cy3 and Cy5 aggregates indicating that the system-bath coupling spectral density in the TDBC aggregate is independent of frequency while the negative sign for rest of the band-edge aggregates indicates an inverse scaling. The scaling laws may be explained by the fact that the excitonic couplings in these systems are quite large (10 3 cm -1 ), and the higher frequency components of system-bath coupling will be highly suppressed in comparison.…”