Coulomb Mediated Hybridization of Excitons in Coupled Quantum Dots.

We report Coulomb mediated hybridization of excitonic states in optically active InGaAs quantum dot molecules. By probing the optical response of an individual quantum dot molecule as a function of the static electric field applied along the molecular axis, we observe unexpected avoided level crossings that do not arise from the dominant single-particle tunnel coupling. We identify a new few-particle coupling mechanism stemming from Coulomb interactions between different neutral exciton states. Such Coulomb resonances hybridize the exciton wave function over four different electron and hole single-particle orbitals. Comparisons of experimental observations with microscopic eight-band k·p calculations taking into account a realistic quantum dot geometry show good agreement and reveal that the Coulomb resonances arise from broken symmetry in the artificial semiconductor molecule.

Energy transport and coherence properties of acoustic phonons generated by optical excitation of a quantum dot.

The energy transport of acoustic phonons generated by the optical excitation of a quantum dot as well as the coherence properties of these phonons are studied theoretically both for the case of a pulsed excitation and for a continuous wave (CW) excitation switched on instantaneously. For a pulsed excitation, depending on pulse area and pulse duration, a finite number of phonon wave packets is emitted, while for the case of a CW excitation a sequence of wave packets with decreasing amplitude is generated after the excitation has been switched on. We show that the energy flow associated with the generated phonons is partly related to coherent phonon oscillations and partly to incoherent phonon emission. The efficiency of the energy transfer to the phonons and the details of the energy flow depend strongly and in a non-monotonic way on the Rabi frequency exhibiting a resonance behavior. However, in the case of CW excitation it turns out that the total energy transferred to the phonons is directly linked in a monotonic way to the Rabi frequency.

Thermodynamics of the asymmetric double sinh-Gordon theory in 1+1 dimensions.

Classical thermodynamics of the (1+1)-dimensional asymmetric double sinh-Gordon system is investigated. The pseudo-Schrödinger equation resulting from the transfer integral method is solved numerically and within the semiclassical approximation; the exact results are also given at several temperatures. It is found that the specific heat exhibits a characteristic hump resembling a similar one observed in the systems with a symmetric potential; in some structures, extremely narrow and extremely high peak is developed. The interpretation for this behavior is given.

Nontopological solitary waves in continuous and discrete one-component molecular chains.

It is shown that the nontopological (bell-shaped) solitary waves in the asymmetric straight phi(4) model are unstable and correspond to saddle points of the potential energy of the continuous system. Their lifetime is estimated. In the discrete model, the potential energy landscape becomes rough: bell-shaped configurations may become stable. The potential energy function is analyzed around the bell-shaped configurations. A dynamical scenario for the decay of the metastable state in a discrete system, related to spontaneous energy localization, is shown.