We present the results of a comparative analysis of the absorption and photoluminescence excitation (PLE) spectra vs. integrated photoluminescence (IPL) measured as a function of the excitation wavelength for a number of samples... more
We present the results of a comparative analysis of the absorption and photoluminescence excitation (PLE) spectra vs. integrated photoluminescence (IPL) measured as a function of the excitation wavelength for a number of samples containing II-VI semiconductor nanocrystals (NCs) produced by different techniques. The structure of the absorption and PL spectra due to excitons confined in NCs and difficulties with the correct interpretation of the transmittance and PLE results are discussed. It is shown that, compared to the conventional PLE, the IPL intensity plotted against the excitation wavelength (EPLE spectra) reproduce better the structure of the absorption spectra. Therefore, IPLE spectroscopy can be successfully used for probing the quantized electron-hole (e-h) transitions in semiconductor nanocrystals.
Bu çalışmada, elektronların akustik fononlar ile etkileşmesinden kaynaklanan kiral polaron oluşumu incelenmiştir. Elektron-fonon sistemlerinin taban durumunu hesaplayabilmek için Lee-Low-Pines teorisi çerçevesinde analitik bir metot... more
Bu çalışmada, elektronların akustik fononlar ile etkileşmesinden kaynaklanan kiral polaron oluşumu incelenmiştir. Elektron-fonon sistemlerinin taban durumunu hesaplayabilmek için Lee-Low-Pines teorisi çerçevesinde analitik bir metot geliştirilmiştir. Grafenin dejenere band yapısının kiral polaron oluşumunu desteklediği tespit edilmiştir.
The Heisenberg’s uncertainty principle can be obtained from the phonon dynamics as follows, from the basic assumptions, of the phonon theory, in a crystal, I have assumed that the atoms of the crystal are spherically symmetric as well as... more
The Heisenberg’s uncertainty principle can be obtained from the phonon dynamics as follows, from the basic assumptions, of the phonon theory, in a crystal, I have assumed that the atoms of the crystal are spherically symmetric as well as the charge distribution on the each of the atoms. Since there are attractive as well repulsive forces acting between the different atoms of a crystal, there might be a definite value of the potential due to this ‘interaction’.
This paper presents a theoretical model for the effect of electron-phonon interaction, temperature and magnetic field on degree of electron spin polarization in GaAs/InAs quantum dot LED. To describe the dynamics, quantum Langevin... more
This paper presents a theoretical model for the effect of electron-phonon interaction, temperature and magnetic field on degree of electron spin polarization in GaAs/InAs quantum dot LED. To describe the dynamics, quantum Langevin equation for photon number and carrier number is used. Simulation results show that degree of electron spin polarization in quantum dot decreases with increase of electron phonon interaction parameter at constant temperature and constant magnetic field which agrees with experimental results in literatures.
This paper presents a theoretical model for the effect of electron-phonon interaction, temperature and magnetic field on degree of electron spin polarization in GaAs/InAs quantum dot LED. To describe the dynamics, quantum Langevin... more
This paper presents a theoretical model for the effect of electron-phonon interaction, temperature and magnetic field on degree of electron spin polarization in GaAs/InAs quantum dot LED. To describe the dynamics, quantum Langevin equation for photon number and carrier number is used. Simulation results show that degree of electron spin polarization in quantum dot decreases with increase of electron phonon interaction parameter at constant temperature and constant magnetic field which agrees with experimental results in literatures.
... These two configurations are expected to have different behavior since, in the latter one, the axial symmetry is broken. We found the energy levels by solving numerically the BenDaniel-Duke equation [ −¯h2 2 ∇ · ( 1 m∗(x, y, z) ∇ ) +... more
... These two configurations are expected to have different behavior since, in the latter one, the axial symmetry is broken. We found the energy levels by solving numerically the BenDaniel-Duke equation [ −¯h2 2 ∇ · ( 1 m∗(x, y, z) ∇ ) + V(x, y, z) ] (x, y, z) = E (x, y, z), (1) ...
This paper presents a theoretical model for the effect of electron - phonon interaction, temperature and magnetic field on degree of electron spin polarization in GaAs/InAs quantum dot LED. To describe the... more
This paper presents a theoretical model for the effect of electron - phonon interaction, temperature and magnetic field on degree of electron spin polarization in GaAs/InAs quantum dot LED. To describe the dynamics, quantum Langevin equation for photon numbe r and carrier number is used. Simulation results show that degree of electron spin polarization in quantum dot decreases with increase of electron phonon interaction parameter at constant temperature and constant magnetic field which agrees with experiment al results in literatures.
Nanocomposites of linear chain of ferroelectric-ferromagnetic crystal structure is considered. It is analyzed theoretically in the motion equation method on the pursuit of magnonic excitations,lattice vibration excitations and their... more
Nanocomposites of linear chain of ferroelectric-ferromagnetic crystal structure is considered. It is analyzed theoretically in the motion equation method on the pursuit of magnonic excitations,lattice vibration excitations and their interactions leading to a new collective mode of excitations,the electormagnons. In this particular work, it is observed that the magnetizations and polarizations are tunable in a given temperature ranges for some specific values of the coupling order parameter.
We study the electron and phonon thermal coupling mechanisms at interfaces between gold films with and without Ti adhesion layers on various substrates via pump-probe time-domain thermoreflectance. The coupling between the electronic and... more
We study the electron and phonon thermal coupling mechanisms at interfaces between gold films with and without Ti adhesion layers on various substrates via pump-probe time-domain thermoreflectance. The coupling between the electronic and the vibrational states is increased by more than a factor of five with the inclusion of an 3 nm Ti adhesion layer between the Au film and the nonmetal substrate. Furthermore, we show an increase in the rate of relaxation of the electron system with increasing electron and lattice temperatures induced by the laser power and attribute this to enhanced electron-electron scattering, a transport channel that becomes more pronounced with increased electron temperatures. The inclusion of the Ti layer also results in a linear dependence of the electron-phonon relaxation rate with temperature, which we attribute to the coupling of electrons at and near the Ti/substrate interface. This enhanced electron-phonon coupling due to electron interface scattering is shown to have negligible influence on the Kapitza conductances between the Au/Ti and the substrates at longer time scales when the electrons and phonons in the metal have equilibrated. These results suggest that only during highly nonequilibrium conditions between the electrons and phonons (Te >> Tp) does electron-phonon scattering at an interface contribute to thermal boundary conductance.
Using a path-integral theory, we study the momentum-specified photoemission spectra (MSPES) of one and two dimensional metallic many-electron systems coupled with Einstein phonons. The multiple scatterings of electrons due to phonons are... more
Using a path-integral theory, we study the momentum-specified photoemission spectra (MSPES) of one and two dimensional metallic many-electron systems coupled with Einstein phonons. The multiple scatterings of electrons due to phonons are shown to completely dominate the MSPES, even if the electron-phonon coupling strength is intermediate. These multiple scatterings result in spectral evolution from a broad Gaussian to a two-headed asymmetric Lorentzian as the momentum changes from the band bottom to the Fermi one (≡pF) . We have also found that this two-headed structure near pF becomes most distinct in the two dimensional non-half-filled cases with no charge density wave gap. These results qualitatively agree with recent experiments of MSPES on the Be(0001) surface and Bi2Sr2CaCu2O8 .