We present a theoretical study of the optical properties quantum dots containing single paramagnetic ion. The eigenvalue problem an electron-hole pair in interaction with localized spin is solved. In Mn-doped nanocrystals II-VI semiconductors such as CdTe fundamental absorption line splits into six components, whose relative intensities strongly depend on Mn orientation respect to polarization light, suggesting possibility detection spin. With atom at center dot overall zero-field splitting...

The photoluminescence spectra of spherical CdTe nanocrystals with zincblende structure are studied by size-selective spectroscopic techniques. We observe a resonant Stokes shift 15 meV when the excitation laser energy is tuned to red side absorption band at 2.236 eV. experimental data analyzed within symmetry-based tight-binding theory exciton spectrum, which first shown account for size dependence fundamental gap reported previously in literature. theoretical presented as function shows...

The optical spectra of CdSe nanocrystals up to 55 \AA{} in diameter are analyzed a wide range energies from the fine structure low-energy excitations so-called high-energy transitions. We apply symmetry-based method two steps. First we take tight-binding (TB) parameters bulk ${\mathrm{sp}}^{3}{s}^{*}$ TB model, extended include spin-orbit interaction. full single-particle obtained an exact diagonalization by using group-theoretical treatment. electron-hole interaction is next introduced:...

We investigate the electronic and magnetic properties of (Ga,Mn)N nanocrystals using density functional theory. study both wurtzite zinc-blende structures doped with one or two substitutional Mn impurities. For a single dopant placed close to surface, behavior empty Mn-induced state, hereafter referred as "Mn hole", is different from bulk (Ga,Mn)N. The energy level corresponding this off-center hole lies within nanocrystal gap near conduction edge. dopants, most stable configuration...

We investigate the electronic and magnetic properties of Mn-doped CdTe nanocrystals (NCs) with $\ensuremath{\sim}2\text{ }\text{nm}$ in diameter which can be experimentally synthesized Mn atoms inside. Using density-functional theory, we consider two doping cases: NCs containing one or impurities. Although $\text{Mn}\text{ }d$ peaks carry five up electrons dot, local moment on site is $4.65{\ensuremath{\mu}}_{B}$. It smaller than $5{\ensuremath{\mu}}_{B}$ because $sp\text{\ensuremath{-}}d$...

We present a novel differential refractive index sensor prototype based on matrix of photonic molecules (PM) soda-lime glass cylinders (εc = 4.5) and two defect cavities. The measured simulated spectra in the microwave range (8-12 GHz) show wide stop band with localized states: reference state, bound to decagonal ring sensing mode is very sensitive permittivity material inserted cavity while state PM remains unperturbed. find that response linear. These results can be extrapolated visible...

The electronic and optical properties of spherical nanoheterostructures are studied within the semi-empirical $sp^{3}s^{*}$ tight-binding model including spin-orbit interaction. We use a symmetry-based approach previously applied to CdSe CdTe quantum dots. complete one-particle spectrum is obtained by using group-theoretical methods. excitonic eigenstates then deduced in configuration-interaction fully taking into account Coulomb direct exchange interactions. Here we focus on ZnS/CdS,...

We investigate acceptor and donor states in GaN nanocrystals doped with a single substitutional impurity. Quantum dots (QD's) of zinc-blende structure spherical shape are considered the radius ranging from 4.5 to 67.7 A. The size-dependent energy spectra calculated within sp3d5s* tight-binding model, which yields good agreement confinement-induced blue shifts observed undoped QD's. computed binding is strongly enhanced respect experimental bulk value when dopant placed at center smallest It...

We investigate the optical properties of (Cd,Mn)Te quantum dots (QDs) by looking at excitons as a function Mn impurities positions and their magnetic alignments. When doped with two impurities, spins, aligned initially antiparallel in ground state, have lower energy parallel configuration for optically active spin-up exciton. Hence, photoexcitation QD state spins induces one them to flip they align parallel. This suggests that QDs are suitable spin-based operations handled light.

We present a novel fabrication process based on laser interference lithography, lift-off and reactive ion etching, which allows us to fabricate periodic nanostructures photovoltaic substrates with an average root mean square (RMS) roughness of 750 nm. unpolished crystalline silicon substrates, reduces their reflectance 30% as fabricated. When additional passivation layer is deposited, the light trapping grows, achieving reduction 60%. In addition, we have successfully integrated...

We theoretically study the role of surfaces in electronic and magnetic properties nanofilms made wurtzite zinc-blende (Ga,Mn)N. The studied doping reactions suggest that Mn impurities replacing Ga cations preferably stay just below unsaturated surface rather than near substrate. hole-mediated ferromagnetism, typical (Ga,Mn)N bulk, is absent from these films, moments for most stable cationic positions become antiferromagnetically coupled. holes ascribed to dopants semiconductors are here...

In this work, the authors present a novel fabrication process to create periodic nanostructures with aspect ratio as high 9.6. These reduce spectral reflectance of silicon less than 4% over broad wavelength region from 200 2000 nm. At visible range spectrum, 650 nm, reflectivity is reduced 0.1%. The and performance that achieved have never been reported before for ordered tapered nanostructures, our knowledge.

The one-band two-dimensional Hubbard Hamiltonian is analyzed using a real-space renormalization-group block method. method, previously applied to the one-dimensional case has been extended two dimensions. It also shown how avoid proliferation of new terms during process if shape blocks and symmetries kept states are chosen conveniently. We characterize ground state by its energy per site, gap charge excitations, double occupancy, effective hopping. system shows an insulating behavior in half...

This paper reports the numerical and experimental study of strain sensing effect bidimensional quasiperiodic structures made with dielectric cylinders. Structures around 100 cylinders arranged following a Penrose disposition were simulated, built measured, in different states deformation. The selected structure contains symmetric decagonal ring resonator that shows two its photonic band gap. frequency these varies linearly opposite directions as is axially deformed, becoming an interesting...

Light confinement induced by resonant states in aperiodic photonic structures are interesting for many applications. A particular case of these resonances can be found 2D quasi-crystalline arrangements dielectric cylinders. These systems present a rather isotropic band gap as well isolated in-gap (as result spatially localized resonances). built high symmetry polygonal clusters that regarded molecules. In this paper we study the transmission properties slab glass cylinders arranged...

Abstract The effects of sp–d exchange interactions on the optical properties quantum dots containing a single Mn ion are investigated within effective mass formalism. quantum‐mechanical eigenvalue problem an electron‐hole pair in interaction with spin is solved analytically. In zinc‐blende semiconductors such as CdTe fundamental absorption line splits into six components, whose relative intensities strongly depend orientation respect to polarization light, suggesting possibility detection...

During the last decades, 2D-ordered and disordered photonic systems have attracted intense attention as capable to control modify flow of light. These structures can also localize light into a bandgap by exciting states arising from cavities, defects, or molecules. We report controllable random system silicon dielectric cylinders that presents deep and, superimposed, two tunable resonant generated decagonal ring resonators embedded it. show high transmission intensity bandwidth remains...

We have studied the electronic structure, exciton states and optical spectra of spherical semiconductor quantum dot wells (QDQW's) by means a symmetry-adapted tight-binding (TB) method. investigated two classes QDQW's: CdS/HgS/CdS, based on CdS core which acts as barrier, with thin HgS well layer intercalated between clad CdS. The second class QDQW's is ZnS cores covered layers act in this case well. calculated values absorption onset show good agreement experimental data. Large...

Photonic Molecules made of dielectric cylinders assembled as two-dimensional octagons and decagons have been studied. These structures exhibit resonance states that change their intensity depending on the incident radiation angle. While most part spectra present small or even null variation, one resonances in both presents a high-sensibility to incidence This strong variation is well described terms electric field distribution this resonant state, which composed maxima with alternate...