Ultrashort phenomena with participation of coherent excitons and biexcitons in crystals
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StatusThe thesis was presented on the 24 November, 2006Approved by NCAA on the 21 December, 2006 Abstract – 0.32 Mb / in romanianThesisCZU 530.145 + 535.14
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Keywords
exciton, biexciton, photon, ultrashort dynamic chaos, nonlinear dynamics, stochastic layerSummary
Some new ultrashort nonlinear phenomena that can be observed in condensed media are studied in the work.
For the first time the occurrence of ultrashort dynamic chaos is studied theoretically owing to the account of nonresonant terms in the interaction Hamiltonian of the coherent quasiparticles in the following models: at the conversion of exciton into biexciton in the M – band range of the semiconductor luminescence, at the two-photon excitation of biexciton from the ground state of a crystal, at the two-photon conversion of exciton into biexciton, and also at the exciton excitation from the ground state of a crystal and coupling of two excitons into a biexciton. Proceeding from the coherent quasiparticle Hamiltonians in representation of secondary quantization, the motion equations in these systems have been received in action-angle variables. Exact analytic solutions were obtained when the nonresonant terms of the coherent quasiparticle interaction Hamiltonians are neglected. The influence of nonresonant terms of the interaction Hamiltonians upon the dynamics of systems was studied. The breakdown of the motion integrals and stochastic layers appearance in the separatrix vicinity were shown to occur under the influence of the nonresonant terms. The stochastic layers’ widths have been estimated theoretically. Depending on the values of the system parameters nonlinear periodic or aperiodic oscillations can arise when the nonresonant terms are neglected, and quasiperiodical or stochastic oscillations arise when nonresonant terms are taken into account. Distances between initially close trajectories and disintegration increments of coherent motion were obtained.
The dynamic properties of excitons and biexcitons have been studied in the ring resonator at exciton excitation from the ground state of a crystal and coupling of two excitons into a biexciton. The Hopf bifurcations and the scenario of transition to chaotic motion regime were found.
For the first time the occurrence of ultrashort dynamic chaos has been studied at intraserial and interserial excitonic transitions in Cu2O type crystals under the influence of an external monochromatic electromagnetic field.
Oficial Reviewers
- Nicolae Enache
doctor habilitat, professor, Institute of Applied Physics of the - Valerii Driuma
doctor
Theses
