arXiv subjects

Tolibjon Abdurakhmonov

Publications and source records attributed to Tolibjon Abdurakhmonov.

3 recordsLinked to original sources

arXiv2026

Davydov Splitting Without a Davydov Pair and Highly Mobile Singlet Excitons in Perylene Red Microcrystals

We investigate the excitonic properties of perylene red microcrystals, whose unit cell contain eight molecules, using both experimental and theoretical methods. Only two of the nominal eight Davydov transitions are experimentally observed, with an apparent splitting of 610 cm$^{-1}$ that is reasonably reproduced by a Frenkel-Holstein exciton model parametrized from density functional theory. A symmetry-based analysis of the eigenstates reveals that the two observed transitions do not belong to the same Davydov pair, so the splitting does not directly report on the Coulomb coupling within the unit cell. The complex mixture of local excitations produces a J-like band for the dominant transitions, favouring exciton transfer through increased spectral overlap. Consistent with this picture, time-correlated single-photon counting of the emission and ultrafast transient absorption spectroscopy show that the dynamics is dominated by highly mobile singlet Frenkel excitons. The exciton mobility extracted from experiment agrees very well with that obtained from Kinetic Monte Carlo simulations, supporting a picture of incoherent hopping transport.

cond-mat.mtrl-sci↗

arXiv2025

Growth of few-layer molecular crystals of PTCDI on hexagonal boron nitride by microspacing air-gap sublimation

Extended two-dimensional (2D) crystals of dye molecules adsorbed on 2D material substrates like boron nitride have recently become a subject of intense study, with potential applications ranging from quantum technology to optoelectronics. The most established technique for the production of these films is physical vapor transport in vacuum. We demonstrate that few-layer crystalline films of the organic dye molecule PTCDI on boron nitride can be produced by microspacing in-air sublimation, a radically simplified technique, not requiring complicated vacuum systems. The resulting layers display clearly resolved atomic step terraces in atomic force microscopy, and a clear polarization anisotropy in their fluorescence, confirming molecular alignment and long-range order. Using density functional theory and classical molecular dynamics simulations, the canted motive is identified as the most likely building block for the morphology of a PTDCI monolayer on the hBN substrate.

cond-mat.mtrl-sci↗

arXiv2022

Self-consistent theory of a homogeneous binary Bose mixture with strong repulsive interspecies interaction

Multicomponent quantum gases are ideal platforms to study fundamental phenomena arising from the mutual interaction between different constituents. Particularly, due to the repulsive interactions between two species, the system may exhibit a phase separation. We develop a mean-field-based theory for a two-component Bose mixture, which is equivalent to the Hartree-Fock-Bogoliubov approximation, and derive analytical expressions for the phase boundary and miscibility. The majority of existing theories, which are valid only for weakly interacting Bose gases, predict that the phase boundary is determined by the criterion $g_{ab}\leqslant\sqrt{g_{aa} g_{bb}}$ (where $g_{ab}$ is a coupling constant between the components $a$ and $b$). We show that in the Bose-Einstein-condensation phase ($T\leqslant T_c$) the system may remain in a stable and miscible phase also for larger values of $g_{ab}$, depending on the gas parameter $γ$ and temperature.

cond-mat.quant-gas↗