arXiv subjects

Sachith Wickramasinghe

Publications and source records attributed to Sachith Wickramasinghe.

3 recordsLinked to original sources

arXiv2026

Mode-Selective and Anharmonicity-Controlled Energy Transport in Cavity-Coupled Water

Recent experiments demonstrate the modification of chemical dynamics via cavity-enhanced vibrational energy transport. Here, we provide a microscopic account of both photonic and mode-selective energy transport using direct mesoscale on-the-fly simulations and provide the mechanistic principles of cavity-modified transport under vibrational strong coupling. We find that molecular anharmonicity plays a crucial role in dictating photonic transport, and driving-dependent photonic localization occurs when coupling cavity modes to a highly anharmonic mode of the molecular system. We demonstrate this in cavity-coupled water by tuning the photon frequency (at normal incidence) close to either the harmonic (or weakly anharmonic) bending mode or the anharmonic stretching modes of water. We confirm our understanding using a simple model system by reproducing the photonic transport and its localization. We also demonstrate that the diffusion of mode-selective temperature, quantified via the variance of the H-O-H bond angle or of the O-H bond length, is highly dependent on the cavity photon frequency. We show that the cavity photon frequency can be used as a tuning knob to achieve and control mode-selective energy transport. We also provide a simple analytical understanding of this phenomenon. Our results highlight the rich dynamical interplay of molecular and photonic degrees of freedom that persist in real atomistic systems.

physics.optics↗

arXiv2025

On-the-Fly Cavity-Molecular Dynamics of Vibrational Polaritons

In this work, we combine the density functional tight-binding (DFTB) approach with a light-matter Hamiltonian beyond the long-wavelength approximation to propagate the dynamics of vibrational polaritons formed by coupling molecular vibrations to confined radiation inside a Fabry-P\'{e}rot optical cavity. Here, we develop a parallelized propagation scheme with lightweight inter-CPU communication by exploiting the sparse nature of the light-matter interactions in the real space representation. We find that the computationally expensive Born charges required for our propagation can be replaced with the computationally inexpensive Mulliken charges to obtain qualitatively accurate linear spectra especially when the nonlinearity (arising from molecular vibrations) of the light-matter interaction term is not substantial. However, the same approach may not be suitable to be used for studying cavity modification of energy transport or chemical dynamics as this approximation leads to spurious heating of the light-matter hybrid system. We demonstrate the utility of this on-the-fly approach to compute angle resolved polaritonic spectra of water. We implement our approach as an open-source computational package, CavOTF, which is available on GitHub.

physics.chem-ph↗

arXiv2025

Mean-field Mixed Quantum-Classical Approach for Many-Body Quantum Dynamics of Exciton-Polaritons

In this work, we use a mixed quantum-classical (mean-field) many-body approach for simulating the quantum dynamics of excitons and exciton-polaritons beyond the single-excitation subspace. We combine the multitrajectory Ehrenfest approach, which propagates slow degrees of freedom classically, with the Gross-Pitaevskii method, which propagates fast degrees of freedom in a mean-field fashion. We use this mean-field many-body Ehrenfest approach to analyze how the phonon-induced dynamic disorder and the many-body interaction affect the incoherent and coherent dynamics of excitons and exciton-polaritons. We examine how the number of excitations and the strength of repulsive exciton-exciton interaction nonlinearly influence the transport, Fr\"ohlich scattering and decoherence.

cond-mat.mtrl-sci↗