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arXiv · 2609.29284

Strong-Field-Driven Non-Linear Electron Dynamics in Thiophene Oligomers

Mustapha Driouech·Caterina Cocchi·Michele Guerrini
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Abstract

The interaction between conjugated molecules and intense electric field pulses drives a plethora of intriguing nonlinear phenomena, including optical limiting. While excited-state absorption was recently identified as the primary mechanism for this effect in thiophene oligomers, open questions remain regarding field-dependent population dynamics under intense laser driving. Using real-time time-dependent density functional theory combined with a determinant-overlap population framework, we track the intensity-dependent nonlinear response of a single thiophene ring (1T) and quaterthiophene (4T) as prototypical members of the oligothiophene family with different length and symmetry. We demonstrate that extended $π$-conjugation in 4T lowers nonlinear excitation thresholds by orders of magnitude compared to 1T. State-resolved population dynamics reveal complete ground-state depletion accompanied by sequential excited-state absorption channels under intense driving. High-harmonic generation spectra explicitly reflect molecular symmetry constraints, while energy-resolved occupation densities confirm continuous orbital redistribution across the $π^*$-manifold. This work provides dynamic physical insights for engineering organic materials with tailored nonlinear optical properties.

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Mustapha Driouech, Caterina Cocchi, Michele Guerrini. 2026-09-24. Strong-Field-Driven Non-Linear Electron Dynamics in Thiophene Oligomers. https://arxiv.org/abs/2609.29284

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