Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userExcitation Induced Dephasing in Semiconductor Quantum Dots
64
0
0.0
(
0
)
Added by
Hans Christian Schneider
Publication date
2003
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
A quantum kinetic theory is used to compute excitation induced dephasing in semiconductor quantum dots due to the Coulomb interaction with a continuum of states, such as a quantum well or a wetting layer. It is shown that a frequency dependent broadening together with nonlinear resonance shifts are needed for a microscopic explanation of the excitation induced dephasing in such a system, and that excitation induced dephasing for a quantum-dot excitonic resonance is different from quantum-well and bulk excitons.
rate research
Read More
Doping of semiconductors by impurity atoms enabled their widespread technological application in micro and opto-electronics. For colloidal semiconductor nanocrystals, an emerging family of materials where size, composition and shape-control offer widely tunable optical and electronic properties, doping has proven elusive. This arises both from the synthetic challenge of how to introduce single impurities and from a lack of fundamental understanding of this heavily doped limit under strong quantum confinement. We develop a method to dope semiconductor nanocrystals with metal impurities providing control of the band gap and Fermi energy. A combination of optical measurements, scanning tunneling spectroscopy and theory revealed the emergence of a confined impurity band and band-tailing. Successful control of doping and its understanding provide n- and p-doped semiconductor nanocrystals which greatly enhance the potential application of such materials in solar cells, thin-film transistors, and optoelectronic devices.
We propose using semiconductor quantum dots for a simulation of chemical reactions as electrons are redistributed among such artificial atoms. We show that it is possible to achieve various reaction regimes and obtain different reaction products by varying the speed of voltage changes applied to the gates forming quantum dots. Considering the simplest possible reaction, $H_2+Hto H+H_2$, we show how the necessary initial state can be obtained and what voltage pulses should be applied to achieve a desirable final product. Our calculations have been performed using the Pechukas gas approach, which can be extended for more complicated reactions.
We propose a scheme to manipulate the spin coherence in vertically coupled GaAs double quantum dots. Up to {em ten} orders of magnitude variation of the spin relaxation and {em two} orders of magnitude variation of the spin dephasing can be achieved by a small gate voltage applied vertically on the double dot. Specially, large variation of spin relaxation still exists at 0 K. In the calculation, the equation-of-motion approach is applied to obtain the electron decoherence time and all the relevant spin decoherence mechanisms, such as the spin-orbit coupling together with the electron--bulk-phonon scattering, the direct spin-phonon coupling due to the phonon-induced strain, the hyperfine interaction and the second-order process of electron-phonon scattering combined with the hyperfine interaction, are included. The condition to obtain the large variations of spin coherence is also addressed.
A dielectric vertical cavity is used to study the spin dynamics of molecularly self-assembled colloidal CdSe quantum dots (QDs). Using this structure, a nearly 30-fold enhancement of Faraday rotation is observed, which scales with the quality factor of the cavity. In this classical nonperturbative regime, the amplified rotation is attributed to optically excited spins interacting with multiple passes of the probe photons in the cavity. By applying this general planar cavity motif to Faraday rotation, dynamical measurements are accessible at extremely low powers on relatively small numbers of quantum confined spins. In CdSe QDs, low power measurements reveal that contributions from exciton and electron spin precession are largely dependent upon the power of excitation. We demonstrate that this scheme is amenable to both soft and hard systems as a means to increase detection sensitivity.
We propose a scheme for a two-qubit conditional phase gate by quantum Zeno effect with semiconductor quantum dots. The system consists of two charged dots and one ancillary dot that can perform Rabi oscillations under a resonant laser pulse. The quantum Zeno effect is induced by phonon-assisted exciton relaxation between the ancillary dot and the charged dots, which is equivalent to a continuous measurement. We solve analytically the master equation and simulate the dynamics of the system using a realistic set of parameters. In contrast to standard schemes, larger phonon relaxation rates increase the fidelity of the operations.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
