Excitonic Mechanism of Local Phase Transformations by Optical Pumping
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Transformations of cooperative electronic states by impacts of optical pumping and/or electrostatic doping is a new mainstream in physics of correlated systems. Here we present a semi-phenomenological modeling of spatio-temporal effects in a system where the light absorption goes through a channel creating the excitons—intra-molecular ones or bound electron–hole pairs—and finally the condensate of optical excitons feeds and stimulates phase transformations. Interacting with a near-critical order parameter and deformations, the excitons are subject to self-trapping. That locally enhances their density which can surpass a critical value to trigger the phase transformation, even if the mean density is below the required threshold. The model can be used e.g. as a simplified version of optically induced neutral-ionic transitions in organic chain compounds.
KeywordsOptical pumping Phase transition Exciton Self-trapping
The authors are grateful for hospitality of the Graduate School of Frontier Sciences at the University of Tokyo, where this work was initiated. We particularly acknowledge very stimulating input from Prof. H. Okamoto and members of his laboratory, and discussions with Prof. N. Nagaosa.
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