Dynamical patterns of phase transformations from self-trapping of quantum excitons

Abstract

Phase transitions induced by short optical pulses is a new mainstream in studies of cooperative electronic states. Its special realization in systems with neutral-ionic transformations stands out in a way that the optical pumping goes to excitons rather than to electronic bands. We present a semi-phenomenological modeling of spacio-temporal effects applicable to any system where the optical excitons are coupled to a symmetry breaking order parameter. In our scenario, after a short initial pulse of photons, a quasi-condensate of excitons appears as a macroscopic quantum state which then evolves interacting with other degrees of freedom prone to instability. This coupling leads to self-trapping of excitons; 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 system is stratified in domains which evolve through dynamical phase transitions and may persist even after the initiating excitons have recombined. We recover dynamic interplays of fields such as the excitons wave function, electronic charge transfer and polarization, lattice deformations.

arXiv commentProceedings of international school-conference on electronic crystals: ECRYS-2014

References in corpus (3)

• Ultrafast switching to a stable hidden topologically protected quantum state in an electronic crystal
• Coherent dynamics of macroscopic electronic order through a symmetry-breaking transition
• Modeling of evolution of a complex electronic system to an ordered hidden state: application to optical quench in TaS2

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• Strong terahertz radiation via rapid polarization reduction in photoinduced ionic-to-neutral transition of tetrathiafulvalene-p-chloranil
• The excitonic insulator route through a dynamical phase transition induced by an optical pulse
• Inhomogeneous Evolution of a Dense Ensemble of Optically Pumped Excitons to a Charge Transfer State