Universal Scalings in Two-Dimensional Anisotropic Dipolar Excitonic Systems

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-similar to 0.5 scaling of the system density of states and predicts unique spectroscopic signatures including: (1) disorder-induced absorption linewidth, W(sigma) similar to sigma(2.8), with sigma the disorder strength, (2) temperature dependent absorption linewidth, W(T) similar to Ts+1.5, with s the exponent of the environment spectral density, and (3) the out-of-plane angular theta dependence of the peak splittings in absorption spectra, Delta E(theta) alpha sin(2) theta. These predictions are confirmed quantitatively with numerical simulations of molecular thin films and tubules.

Automated summary

The study investigates the anisotropic dispersion properties of 2D dipolar excitonic systems, revealing linear energy dispersion in the in-plane direction and dispersionless behavior in the perpendicular direction, with unique spectroscopic signatures predicted.