M. O. Nestoklon

Ioffe Institute | ioffe

The tunability of the optical properties of lead halide perovskite nanocrystals makes them highly appealing for applications. Halide anion exchange and quantum confinement enable tailoring of the band gap. For spintronics, the Landé g-factors of electrons and holes are essential. Using empirical tight-binding and k·p methods, we calculate them for...

Optical orientation of carrier spins by circularly polarized light is the basis of spin physics in semiconductors. Here, we demonstrate strong optical orientation of 85\%, approaching the ultimate limit of unity, for excitons in FA$_{0.9}$Cs$_{0.1}$PbI$_{2.8}$Br$_{0.2}$ lead halide perovskite bulk crystals. Time-resolved photoluminescence allows us...

The tunability of the optical properties of lead halide perovskite nanocrystals makes them highly appealing for applications. Both, halide anion exchange and quantum confinement pave the way for tailoring their band gap energy. For spintronics applications, the Land{\'e} g-factors of electrons and hole are of great importance. By means of the empir...

The Landé or g factors of charge carriers in solid state systems provide invaluable information about the response of quantum states to external magnetic fields and are key ingredients in the description of spin-dependent phenomena in nanostructures. We report on a comprehensive theoretical analysis of electron and hole g factors in lead chalcogeni...

The Land\'e or g-factors of charge carriers in solid state systems provide invaluable information about response of quantum states to external magnetic fields and are key ingredients in description of spin-dependent phenomena in nanostructures. We report on the comprehensive theoretical analysis of electron and hole g-factors in lead chalcogenide n...

We propose the concept of valley coherence and superradiance in the reciprocal space and show that it leads to an N-fold decrease of the bright exciton radiative lifetime in quantum dots (QDs) of an N-valley semiconductor. Next we explain why, despite this, the exciton radiative lifetimes in PbX (X= S, Se, Te) QDs, measured from the photoluminescen...

The interaction between an exciton and acoustic phonons via the deformation potential in PbS nanocrystals is calculated in the k·p model. It is shown that the anisotropy of the deformation potential leads to nonzero interaction of an exciton with spheroidal phonons with the total angular momentum j=2. The size dependence of the Huang-Rhys factors f...

The Landé or g-factors of charge carriers are decisive for the spin-dependent phenomena in solids and provide also information about the underlying electronic band structure. We present a comprehensive set of experimental data for values and anisotropies of the electron and hole Landé factors in hybrid organic-inorganic (MAPbI3, MAPb(Br0.5Cl0.5)3,...

Theory of weak localization is developed for two-dimensional holes in the presence of in-plane magnetic field. The Zeeman splitting even in the hole momentum results in the spin-dependent phase changing the quantum interference. The negative correction to the conductivity is shown to decrease by a factor of two by the in-plane magnetic field. The p...

No PDF available ABSTRACT From measured magnetic field dependences of attenuation and velocity of surface acoustic waves (SAW), we calculated the real part of electron the conductivity in a 75-nm-wide n-GaAs/AlGaAs quantum well in magnetic fields of up to 18 T at frequencies of 30–300 MHz in the temperature range 20–500 mK. We observed slow magneto...

The interaction between exciton and acoustic phonons via deformation potential in PbS nanocrystals is calculated in the extended ${\bf k} \cdot {\bf p}$ model. The size-dependence of the Huang-Rhys factors for the fundamental breathing mode and its overtones as well as for spheroidal vibrations with the total angular momentum $j=2$ are evaluated.

We propose the concept of valley coherence and superradiance in the reciprocal space and show that it leads to an $N$-fold decrease of the bright exciton radiative lifetime in quantum dots (QDs) of an $N$-valley semiconductor. Next we explain why, despite this, the exciton radiative lifetimes in PbX (X = S, Se, Te) QDs, measured from the photolumin...

The Land\'e or $g$-factors of charge carriers are decisive for the spin-dependent phenomena in solids and provide also information about the underlying electronic band structure. We present a comprehensive set of experimental data for values and anisotropies of the electron and hole Land\'e factors in hybrid organic-inorganic (MAPbI$_3$, MAPb(Br$_{...

Band structure of inorganic lead halide perovskites is substantially different from the band structure of group IV, III–V and II–VI semiconductors. However, the standard empirical tight-binding model with sp3d5s∗ basis gives nearly perfect fit of band structure calculated in the density functional theory. The tight-binding calculations of ultrathin...

The spin-orbit interaction of two-dimensional (2D) electrons in semiconductor quantum wells gives rise to a variety of interesting transport and optical spin-dependent effects. In the GaAs/AlGaAs type heterosystems, this interaction consists of the isotropic Bychkov-Rashba term, which is absent in symmetric wells, and the anisotropic Dresselhaus te...

In this work we investigate effects of the crystal phase, twinning defects and shell formation on the work function distribution over the surface of axially heterostructured GaP/GaPAs/GaP nanowires via frequency-modulated Kelvin probe force microscopy. Analysis of experimental data is supported by theoretical model based on density functional theor...

A low‐temperature polarization‐resolved magneto‐photoluminescence experiment is performed on individual PbS/CdS core/shell quantum dots (QDs). The experiment enables a direct measurement of the exciton Landé g factor and the anisotropic zero‐field splitting of the lowest emissive bright exciton triplet in PbS/CdS QDs. While anisotropic splittings o...

Band structure of inorganic lead halide perovskites is substantially different from the band structure of group IV, III-V and II-VI semiconductors. However, the standard empirical tight-binding model with sp3d5s* basis gives nearly perfect fit of band structure calculated in the density functional theory. The tight-binding calculations of ultrathin...

DOI:https://doi.org/10.1103/PhysRevB.102.239902

The spin-orbit interaction of two-dimensional (2D) electrons in semiconductor quantum wells is usually considered to be determined by the band profile of a heterostructure. In the GaAs/AlGaAs type heterosystems, this interaction consists of the isotropic Bychkov-Rashba term, which is absent in symmetric wells, and the anisotropic Dresselhaus term,...

We study the exciton fine structure in quantum dots of multivalley lead chalcogenides. We demonstrate that intervalley electron-hole exchange interaction, ignored in previous studies, dramatically modifies the exciton fine structure and leads to appearance of the ultrabright valley-symmetric spin-triplet exciton state dominating interband optical a...

Using the atomistic sp3d5s∗ tight-binding method, we calculate the optical absorption spectra due to phononless optical transitions in Si, Ge, and SiGe alloy nanocrystals embedded in an amorphous dielectric SiO2 matrix. For the SiO2 matrix, we use a virtual crystal approximation assuming the cubic crystalline structure, similar to β crystobalite, i...

The DFT calculations of energy profiles for the carbon monoxide oxidation reaction in the presence of Ni catalyst in the various electric fields were performed by means of the Gaussian package. In order to do that the simple computational model was suggested for the active sites on the surface of the Ni catalyst prepared by the laser electrodispers...

Systematic studies of the effect of the electron concentration on the Raman spectra of single-layer graphene films have been carried out. The samples were grown by thermal destruction of the Si-face of the 4H-SiC substrate. Analysis of the results led us to the conclusion that for the correct estimation of the electron concentration and strain valu...

Fascinating optical properties governed by extremely confined excitons have been so far observed in 2D crystals like monolayers of transition metal dichalcogenides. These materials, however, are limited for production by epitaxial methods. Besides, they are not suitable for the development of optoelectronics for challenging deep ultraviolet spectra...

With a tunable size-dependent photoluminescence (PL) over a wide infrared wavelength range, lead chalcogenide quantum dots (QDs) have attracted significant scientific and technological interest. Nevertheless, the investigation of intrinsic exciton photophysics at the single-QD level has remained a challenge. Herein, we present a comprehensive study...

Comprehensive study of high-quality monolayer graphene samples grown by thermal destruction of the Si-face of the 4 H -SiC substrate was carried out. Analysis of the data obtained by Raman spectroscopy and angle-resolved photoemission spectroscopy suggest the need to use the Fermi velocity in the graphene layer under study to obtain a correct estim...

We develop the empirical tight binding approach for the modeling of electronic states and optical properties of Si nanocrystals embedded in SiO2 matrix. To simulate the wide band gap SiO2 matrix we use the virtual crystal approximation. The tight-binding parameters of the material with the diamond crystal lattice are fitted to the band structure of...

Oscillations of the real component of AC conductivity σ1 in a magnetic field were measured in the n-AlGaAs/GaAs structure with a wide (75 nm) quantum well by contactless acoustic methods at T=(20-500)~mK. In a wide quantum well, the electronic band structure is associated with the two-subband electron spectrum, namely the symmetric (S) and antisymm...

In the empirical tight-binding approach we study the electronic states in spherical SiGe nanocrystals embedded in SiO2 matrix. For the SiGe alloy and the matrix we use the virtual crystal approximation. The energy and valley structure of electron states is obtained as a function of Ge composition and nanocrystal size. Calculations show that the mix...

In the empirical tight-binding approach we study the electronic states in spherical SiGe nanocrystals embedded in SiO2 matrix. The energy and valley structure is obtained as a function of Ge composition and nanocrystal size. The calculations show that the mixing of hot electrons in the nanocrystal with electrons in wide band gap matrix is possible...

Oscillations of the real component of AC conductivity $\sigma_1$ in a magnetic field were measured in the n-AlGaAs/GaAs structure with a wide (75 nm) quantum well by contactless acoustic methods at $T$=(20-500)~mK. Deep oscillations corresponding to the integer and half-integer filling factors were observed. The appearance of oscillations with half...

The problem of the optimal choice of parameters of the empirical tight-binding method to simulate the quantum-confined levels of Si nanocrystals embedded into an amorphous SiO2 matrix is studied. To account for tunneling from nanocrystals to SiO2, the amorphous matrix is considered as a virtual crystal with a band structure similar to that of SiO2...

We demonstrate the optical orientation and alignment of excitons in a two-dimensional layer of CsPbI$_3$ perovskite nanocrystals prepared by colloidal synthesis and measure the anisotropic exchange splitting of exciton levels in the nanocrystals. From the experimental data at low temperature (2K), we obtain the average value of anisotropic splittin...

Emerging part of condensed matter science, which deals with the systems of extreme two-dimensionality, renews the interest in natural 2D objects such as planar stacking faults (SFs) in semiconductor crystals. We report on the observation of an excitonic state localized at the 1D intersection of the SF with a high quality ZnSe quantum well (QW). The...

Slow magnetooscilations of the conductivity are observed in a 75 nm wide quantum well at heating of the two-dimensional electrons by a high-intensity surface acoustic wave. These magnetooscillations are caused by intersubband elastic scattering between the symmetric and asymmetric subbands formed due to an electrostatic barrier in the center of the...

This review is devoted to the modeling of Si and Ge nanocrystals by means of the tight-binding method. First we give the short outline of the modeling methods and their application for the discription of silicon and germanium nanocrystals. Then, the tight-binding method with extended s, p, d, and s* basis is explained in details and the results obt...

We use an empirical tight-binding approach to calculate electron and hole states in [111]-grown PbSe nanowires. We show that the valley-orbit and spin-orbit splittings are very sensitive to the atomic arrangement within the nanowire elementary cell and differ for [111]-nanowires with microscopic $D_{3d}$, $C_{2h}$ and $D_{3}$ symmetries. For the na...

We have studied the electronic properties of epitaxial graphene devices patterned in a meander shape with the length up to a few centimeters and the width of few tens of microns. These samples show a pronounced dependence of the resistance on temperature. Accurate comparison with theory shows that this temperature dependence originates from the wea...

We present the tight binding calculations of the lead selenide nanowires: energy spectra of quantum confined states as a function of nanowire radius, dispersion in the full Brillouin zone, and the radial part of local electronic state density, which helps us to recognise valley splitting in the spectra. Also, we compare our results to KP perturbati...

An effective Hamiltonian of silicene in the neighborhood of Dirac points in the presence of electric and magnetic fields perpendicular to the plane of the film is constructed on the basis of symmetry analysis. Numerical coefficients of various terms in the Hamiltonian are obtained by the tight binding method in the basis sp³d⁵s* with regard to the...

We show that for lattice-mismatched zinc-blende-type (110)-grown quantum wells a significant contribution to the zero-magnetic-field spin splitting of electron subbands comes from strain-induced spin-orbit coupling. Combining envelope function theory and atomistic tight-binding approach we calculate spin-orbit splitting constants for realistic quan...

We present a theoretical study of Ge-core/Si-shell nanocrystals in a wide bandgap matrix and compare the results with experimental data obtained from the samples prepared by co-sputtering. The empirical tight-binding technique allows us to account for the electronic structure under strain on the atomistic level. We find that a Si shell as thick as...

We study the complex electronic band structure of low In content InGaAs/GaP quantum dots. A supercell extended-basis tight-binding model is used to simulate the electronic and the optical properties of a pure GaAs/GaP quantum dot modeled at the atomic level. Transitions between hole states confined into the dots and several XZ-like electronic state...

The spin-orbit interaction of 2D electrons in the quantum wells grown from the III-V semiconductors consists of the two parts with different symmetry: the Bychkov-Rashba and the Dresselhaus terms. The last term is usually attributed to the bulk spin-orbit Hamiltonian which reflects the Td symmetry of the zincblende lattice. While it is known that t...

We show that a significant contribution to the spin-orbit splitting of electron subbands in (110)-grown quantum wells (QWs) comes from the strain-related splitting of the bulk conduction band which emerges due to a lattice mismatch between the QW and buffer layer crystals. We use the atomistic tight-binding approach to calculate the spin splitting...

We propose a novel approach to construct the empirical tight-binding parameters of ternary alloys in the virtual crystal approximation. It combines a compact formulation of the strain parameters and a linear interpolation of the hamiltonians of strained binary materials. We obtain a perfect description of the bandgap bowing of ternary alloys in the...

We present a theoretical study of Ge-core/Si-shell nanocrystals in a wide bandgap matrix and compare the results with experimental data obtained from the samples prepared by co-sputtering. The empirical tight-binding technique allows us to account for the electronic structure under strain on the atomistic level. We find that a Si shell as thick as...

We propose a simple and effective approach to construct the empirical tight-binding parameters of ternary alloys in the virtual crystal approximation. This combines a new, compact formulation of the strain parameters and a linear interpolation of the hamiltonians of binary materials strained to the alloy equilibrium lattice parameter. We show that...

Energy spectra both of the conduction and valence bands of the HgTe quantum wells with a width close to the Dirac point were studied experimentally. Simultaneous analysis of the Shubnikov-de Haas oscillations and Hall effect over a wide range of electron and hole densities gives surprising result: the top of the valence band is strongly split by sp...

The electronic structure of silicene is simulated by the tight binding method with the basis sp 3d 5s*. The results are in good agreement with ab initio calculations. The effective Hamiltonian of silicene in the vicinity of the Dirac point is constructed by the method of invariants. Silicon atoms in silicene are located in two parallel planes displ...

The properties of neutral acceptor states in GaAs are re-examined in the frame of extended-basis &$s{{p}^{3}}{{d}^{5}}{{s}^{*}}$; tight-binding model. Spherical harmonics decomposition of microscopic local density of states (LDOS) allows for the direct analysis of the tight-binding results in terms of k · p approximation. Lifting of degeneracy by s...

We examine the possibility of intrinsic interface states bound to the plane of In-Sb chemical bonds at InAs/AlSb interfaces. Careful parameterization of the bulk materials in the frame of the extended basis spds^* tight-binding model and recent progress in predictions of band offsets severely limit the span of tight-binding parameters describing th...

We describe the fine structure of Dirac states in HgTe/CdHgTe quantum wells of critical and close-to-critical thickness and demonstrate the formation of an anticrossing gap between the tips of the Dirac cones driven by interface inversion asymmetry. By combining symmetry analysis, atomistic calculations, and k-p theory with interface terms, we obta...

Expressions for Mueller matrices describing how the reflection from plane mirrors with an arbitrary orientation of the surface affects the polarization are obtained. The expressions can be useful in considering new ellipsometers’ optical schemes containing plane mirrors, as well as mirrors with a nonzero curvature of the surface.

We put forward a theory of the weak localization in two dimensional graphene layers which explains experimentally observable transition between positive and negative magnetoresistance. Calculations are performed for the whole range of classically weak magnetic field with account on intervalley transitions. Contribution to the quantum correction whi...

CdSe nanoplatelets show perfectly quantized thicknesses of a few monolayers. They present a situation of extreme, yet well defined quantum confinement. Due to a large dielectric contrast between the semiconductor and its ligand environment, interaction between carriers and their dielectric images strongly renormalize bare single particle states. We...

The properties of neutral acceptor states in zinc-blende semiconductors are re-examined in the frame of extended-basis $sp^3d^5s^*$ tight-binding model. The symmetry discrepancy between envelope function theory and atomistic calculations is explained in terms of over symmetric potential in current k$\cdot$p approaches. Spherical harmonics decomposi...

The nature of the ground optical transition in (In, Ga)As/GaP quantum dots is thoroughly investigated through k·p calculations and a supercell tight-binding simulation. Quantum dot morphology is deduced from scanning-tunneling-microscopy images. The strain field has a strong influence on the conduction band states. Indeed, for a pure GaAs QD, the w...

CdSe nanoplatelets show perfectly quantized thicknesses of few monolayers. They present a situation of extreme, yet well defined quantum confinement. Due to large dielectric contrast between the semiconductor and its ligand environment, interaction between carriers and their dielectric images strongly renormalize bare single particle states. We dis...

The nature of the ground optical transition in an (In,Ga)As/GaP quantum dot is thoroughly investigated through a million atoms supercell tight-binding simulation. Precise quantum dot morphology is deduced from previously reported scanning-tunneling-microscopy images. The strain field is calculated with the valence force field method and has a stron...

We present the theory of fine structure of electron states in symmetric and asymmetric zinc-blende-type quantum wells with the (110) crystallographic orientation. By combining the symmetry analysis, sp 3 d 5 s* tight-binding method, and envelope-function approach we obtain quantitative description of in-plane wave vector, well width and applied el...

The spin-dependent electron-phonon scattering in the L and Γ valleys of germanium crystals has been investigated theoretically. For this purpose, the 16 × 16 k · p Hamiltonian correctly describing the electron dispersion in the vicinity of the L point of the Brillouin zone in germanium in the lowest conduction bands and the highest valence bands ha...

It is well known that the quantum correction to the conductivity in graphene may show a transition from weak-localization to weak-antilocalization regime. We develop a non-diffusion theory of the weak localization in graphene and consider the interplay between weak antilocalization due to intravalley scattering and weak localization due to interval...

Electron spin polarization up to 100% has been observed in type-II narrow-gap heterostructures with ultrathin InSb insertions in an InAs matrix via investigation of circularly polarized photoluminescence in an external magnetic field applied in Faraday geometry. The polarization degree decreases drastically, changes its sign, and saturates finally...

We investigate the spin-dependent electron-phonon scatterings of the $L$ and $\Gamma$ valleys and the band structure near the conduction band minima in germanium. We first construct a $16\times16$ ${\bm k}\cdot{\bm p}$ Hamiltonian in the vicinity of the $L$ point in germanium, which ensures the correctness of the band structure of the lowest three...

(In,Ga)As/GaP(001) quantum dots (QDs) are grown by molecular beam epitaxy and studied both theoretically and experimentally. The electronic band structure is simulated using a combination of k.p and tight-binding models. These calculations predict an indirect to direct crossover with the In content and the size of the QDs. The optical properties ar...