Persistent spectral hole burning in semiconductor nanocrystals

journal articl

EXCITON-PHONON INTERACTION AND PHONON FREQUENCY SHIFT IN QUANTUM DOTS

We present a theory of LO phonon renormalization by coupling with the excitonin semiconductor quantum dots. We find that the one phonon side band of theexciton ground state shows an anticrossing with the excited exciton states. Evenaway from such a resonant coupling, the phonon frequency shift is significant.For example, in CuCl quantum dots in the weak confinement regime, the phononfrequency in the presence of a single exciton is reduced by about 10% from its valuein the ground state. Similar results are predicted for CdS and GaAs quantum dotsin the strong confinement regime.24th International Conference on the Physics of Semiconductors : Jerusalem, Israel August 2-7, 199

LO Phonon Renormalization in Optically Excited CuCl Nanocrystals

We have revealed sharp structures in the absorption spectrum of CuCl nanocrystals using persistent hole-burning spectroscopy and observed sidebands due to phonon-assisted absorption. The LO phonon frequency in the excited state of the nanocrystal is reduced by about 10% from the free value due to mixing with the exciton. When the mixing becomes resonant, the phonon sideband anticrosses with the excited exciton state. We present a theory of the phonon renormalization in nanocrystals and obtain results in excellent agreement with the experiment

VIBRATION PROTECTION OF POWERFUL INDUCTORS

Electrodynamic and vibroacoustic problems during induction heating of solids with variable curvature of surface - primarily heating of slabs for rolling - are viewed. It is recommended to perform electrodynamic calculation on numerical model developed through coupled circuits method and virtual displacement law. For numerical solution of vibration problem it is worth to use finite-element method. In the general case for calculating of distributed forces Biot-Savart-Laplaces law is used. This law permits to definite surface current density in a slab. Through inductor vibration model studies the form of inductor optimal shell is synthesized according to the criterion of minimal noise emissions.</jats:p

WAYS OF ENERGY SAVING

The article views energy saving as motive force for sustainable economic growth in Russia. Electrical energy is a product which determines performance indicators of industrial enterprises, production quality, equipment and apparatus reliability and even mental health of people. The role of education and competence development in the fi eld of energy saving is highlighted. The optimization of energy intensive technologies is also very eff ective. The authors prove that electrical energy is the most ecological energy form, it is more eff ective for usage than mineral fuel. Possible ways of energy saving are studied at operating objects as well as objects in design.</jats:p

Observation of persistent spectral hole–burning in semiconductor nanocrystals

So far, persistent spectral hole-burning (PSHB) phenomenon has been observed in a number of materials. They are molecules in glasses, crystals and polymers, color centers in alkali halide crystals, and rare earth and transition metal ions in glasses and crystals. They are molecular or ionic guests embedded in glass, crystal or polymer hosts. Basic requirements for the PSHB are summarized as follows: (1) The optical absorption of guests embedded in hosts must be broadened inhomogeneously. (2) There must exist more than one ground state configurations of the total system consisting of guests and hosts. (3) The relaxation among the ground states must be slower than the decay rate of any excited state. In fact, this set of requirements is satisfied in many kinds of molecular or ionic guests in hosts, such as glasses, crystals and polymers, at low temperatures. We can naturally understand that guests consisting of small number of atoms are greatly influenced by the surrounding hosts and that the energy levels of the guests are inhomogeneously broadened.</jats:p