Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNovel size effects on magneto-optics in the spherical quantum dots
84
0
0.0
(
0
)
Authors
Manvir S. Kushwaha
Ask ChatGPT about the research
No Arabic abstract
We embark on investigating the magneto-optical absorption in {em spherical} quantum dots {em completely} confined by a harmonic potential and exposed to an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines RPA that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. Intensifying the confinement or magnetic field and reducing the dot-size yields a blue-shift in the absorption peaks. However, the size effects are seen to be predominant in this role. The magnetic field tends to maximize the localization of the particle, but leaves the peak position of the radial distribution intact. The intra-Landau level transitions are forbidden.
rate research
Read More
Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting {em spherical} quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level transitions are seen to be forbidden. The spherical quantum dots have an edge over the strictly two-dimensional quantum dots in that the additional (magnetic) quantum number makes the physics richer (but complex). A deeper grasp of the Coulomb blockade, quantum coherence, and entanglement can lead to a better insight into promising applications involving lasers, detectors, storage devices, and quantum computing.
A deeper sense of advantages over the planar quantum dots and the foreseen applications in the single-electron devices and quantum computation have given vertically stacked quantum dots (VSQD) a width of interest. Here, we embark on the collective excitations in a quantum wire made-up of vertically stacked, self-assembled InAs/GaAs quantum dots in the presence of an applied magnetic field in the symmetric gauge. We compute and illustrate the influence of an applied magnetic field on the behavior characteristics of the density of states, Fermi energy, and collective (magnetoplasmon) excitations [obtained within the framework of random-phase approximation (RPA)]. The Fermi energy is observed to oscillate as a function of the Bloch vector. Remarkably, the intersubband single-particle continuum splits into two with a collective excitation propagating within the gap. This is attributed to the (orbital) quantum number owing to the applied magnetic field. Strikingly, the alteration in the well- and barrier-widths can enable us to customize the excitation spectrum in the desired energy range. These findings demonstrate, for the very first time, the viability and importance of studying the VSQD subjected to an applied magnetic field. The technological promise that emerges is the route to devices exploiting magnetoplasmon qubits as the potential option in designing quantum gates for the quantum communication networks.
The magnetic field dependence of the excitonic states in unstrained GaAs/AlGaAs quantum dots is investigated theoretically and experimentally. The diamagnetic shift for the ground and the excited states are studied in magnetic fields of varying orientation. In the theoretical study, calculations are performed within the single band effective mass approximation, including band nonparabolicity, the full experimental three-dimensional dot shape and the electron-hole Coulomb interaction. These calculations are compared with the experimental results for both the ground and the excited states in fields up to 50 Tesla. Good agreement is found between theory and experiment.
Using a combination of continuous wave and time-resolved spectroscopy, we study the effects of interfacial conditions on the radiative lifetimes and photoluminescence intensities of colloidal CdTe/CdS quantum dots (QDs) embedded in a three-dimensional nanostructured silicon (NSi) matrix. The NSi matrix was thermally oxidized under different conditions to change the interfacial oxide thickness. QDs embedded in a NSi matrix with ~0.5 nm of interfacial oxide exhibited reduced photoluminescence intensity and nearly five times shorter radiative lifetimes (~16 ns) compared to QDs immobilized within completely oxidized, nanostructured silica (NSiO2) frameworks (~78 ns). Optical absorption by the sub-nm oxidized NSi matrix partially lowers QD emission intensities while non-radiative carrier recombination and phonon assisted transitions influenced by defect sites within the oxide and NSi are believed to be the primary factors limiting the QD exciton lifetimes in the heterostructures.
We present a detailed investigation into the optical characteristics of individual InAs quantum dots (QDs) grown by metalorganic chemical vapor deposition, with low temperature emission in the telecoms window around 1300 nm. Using micro-photoluminescence (PL) spectroscopy we have identified neutral, positively charged, and negatively charged exciton and biexciton states. Temperature-dependent measurements reveal dot-charging effects due to differences in carrier diffusivity. We observe a pronounced linearly polarized splitting of the neutral exciton and biexciton lines (~250 ueV) resulting from asymmetry in the QD structure. This asymmetry also causes a mixing of the excited trion states which is manifested in the fine structure and polarization of the charged biexciton emission; from this data we obtain values for the ratio between the anisotropic and isotropic electron-hole exchange energies of (Delta1)/(Delta0)= 0.2--0.5. Magneto-PL spectroscopy has been used to investigate the diamagnetic response and Zeeman splitting of the various exciton complexes. We find a significant variation in g-factor between the exciton, the positive biexciton, and the negative biexciton; this is also attributed to anisotropy effects and the difference in lateral extent of the electron and hole wavefunctions.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
