2016/02/18 by Raffaele Tavarone, Patrick Charbonneau, Holger Stark
Chemistry · Materials Science · Physics and Astronomy · #Birefringence #Chemical physics #Chemistry #Classical mechanics #Computational chemistry #Exponential decay #Isomerization #Isotropy #Kinetic Monte Carlo #Kinetic energy #Liquid Crystal Research Advancements #Materials science #Mechanical and Optical Resonators #Molecular dynamics #Molecular physics #Molecule #Monolayer #Monte Carlo method #Nanotechnology #Optics #Physics #Power law #Relaxation (psychology) #Spectroscopy and Quantum Chemical Studies #cond-mat.soft #cond-mat.stat-mech #physics.chem-ph
paper · pdf · doi:10.1063/1.4943393
published as J. Chem. Phys. 144, 104703 (2016) · 14 pages, 12 figures
arxiv created 2016/02/18 · openalex publication_date 2016/03/11 · arxiv updated 2016/03/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Recent experiments have demonstrated that in a dense monolayer of photo-switchable dye methyl-red molecules the relaxation of an initial birefringence follows a power-law decay, typical for glass-like dynamics. The slow relaxation can efficiently be controlled and accelerated by illuminating the monolayer with circularly polarized light, which induces trans-cis isomerization cycles. To elucidate the microscopic mechanism, we develop a two-dimensional molecular model in which the trans and cis isomers are represented by straight and bent needles, respectively. As in the experimental system, the needles are allowed to rotate and to form overlaps but they cannot translate. The out-of-equilibrium rotational dynamics of the needles is generated using kinetic Monte Carlo simulations. We demonstrate that, in a regime of high density and low temperature, the power-law relaxation can be traced to the formation of spatio-temporal correlations in the rotational dynamics, i.e., dynamic heterogeneity. We also show that the nearly isotropic cis isomers can prevent dynamic heterogeneity from forming in the monolayer and that the relaxation then becomes exponential.