Kirill N. Boldyrev

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• PhD
• Professor (Full) at Beijing Institute of Technology

Far-infrared reflection and ellipsometry measurements on multiferroic PrFe3(BO3)4 and SmFe3(BO3)4 single crystals were used to investigate the interaction between lattice phonons and electronic excitations associated with 4f crystal-field transitions. A temperature-dependent interference between two types of excitations was observed in PrFe3(BO3)4...

Magnetic control of the crystal chirality was announced by Saito et al. [Phys. Rev. Lett. 101, 117402 (2008)] on the ground of experiments in CuB2O4. This claim has raised a sharp dispute in the literature because it seemed to contradict the fundamental symmetry principles. We settle this dispute on the basis of a high-resolution optical spectrosco...

We report on a new effect caused by the electron-phonon coupling in a stoichiometric rare-earth antiferromagnetic crystal subjected to an external magnetic field, namely, the appearance of a nonzero gap in the spectrum of electronic excitations in an arbitrarily small field. The effect was registered in the low-temperature far-infrared (terahertz)...

We have investigated the hyperfine structure in high-resolution broadband optical absorption spectra of a strongly diluted paramagnet LiYF47:Ho3+ (0.1 at. %) in external magnetic fields parallel to the tetragonal symmetry axis of the crystal. Anticrossings in the hyperfine spectral pattern were observed. It is the first direct observation of the hy...

Resolved hyperfine structure and narrow inhomogeneously broadened lines in the optical spectra of a rare-earth-doped crystal are favorable for the implementation of various sensors. Here, a well-resolved hyperfine structure in the photoluminescence spectra of LiYF 4 :Ho single crystals and the anticrossings of hyperfine levels in a magnetic field a...

Исследованы спектры пропускания инфракрасного и видимого излучения монокристаллическими вискерами TiS3 при разных поляризациях света в диапазоне температур от комнатной до гелиевой. Определены абсолютные значения коэффициента поглощения. В области дальнего инфракрасного излучения наблюдались неизвестные ранее фононные моды. Изучена зависимость шири...

Transmission spectra of TiS 3 single crystal whiskers in the infrared and optical bands have been studied at various light polarizations in the temperature range from room to liquid helium. The absolute absorption coefficients have been determined. Previously unknown phonon modes have been observed in the far infrared region. The study of the tempe...

Rare-earth orthoferrites are a promising platform for antiferromagnetic spintronics with a rich variety of terahertz spin and lattice dynamics phenomena. For instance, it has been experimentally demonstrated that the light-driven optical phonons can coherently manipulate macroscopic magnetic states via nonlinear magnetophononic effects. Here using...

Rare-earth orthoferrites are a promising platform for antiferromagnetic spintronics with a rich variety of terahertz spin and lattice dynamics phenomena. For instance, it has been experimentally demonstrated that the light-driven optical phonons can coherently manipulate macroscopic magnetic states via nonlinear magnetophononic effects. Here using...

The coupling between antiferromagnetic spins and infrared-active phonons in solids is responsible for many intriguing phenomena and is a field of intense research with extensive potential applications in the modern devices based on antiferromagnetic spintronics and phononics. Insulating rutile antiferromagnetic crystal CoF2 is one of the model mate...

The coupling between antiferromagnetic spins and infrared-active phonons in solids is responsible for many intriguing phenomena and is a field of intense research with extensive potential applications in the modern devices based on antiferromagnetic spintronics and phononics. Insulating rutile antiferromagnetic crystal CoF$_2$ is one of the model m...

Solvothermal reaction of magnesium nitrate and boron oxide in N,N-dimethylformamide produced a number of particularly complex supramolecular magnesium borates. Five topologically different types of negatively charged {Mg@[B18φ34-35]}-clusters, φ = O, OH, were observed with the magnesium cation as a core and octadecaborate anions as shells. The clus...

The Sm3+/Gd3+ co-doped glasses in the B2O3–GeO2–PbO and B2O3–GeO2–Bi2O3 systems have been synthesized in the composition range of 40B2O3–40GeO2–(15-17)PbO(Bi2O3)–(3-2)Sm2O3–(2-1)Gd2O3 and 42.5B2O3–42.5GeO2–(11.25-12.75)PbO(Bi2O3)–(2.25-1.5)Sm2O3–(1.5-0.075)Gd2O3. The physical, structural, and spectral properties of the produced glasses have been st...

Flavins such as flavin mononucleotide or flavin adenine dinucleotide are bound by diverse proteins, yet have very similar spectra when in the oxidized state. Recently, we developed new variants of flavin‐binding protein CagFbFP exhibiting notable blue (Q148V) or red (I52V A85Q) shifts of fluorescence emission maxima. Here, we use time‐resolved and...

he high-resolution optical absorption spectra of NdFe3(BO3)4 single crystals have been recorded at temperatures from 4 to 40 K in the IR range of f–f transitions in a Nd3+ ion. Light linearly polarized at different angles to the C2 axes in the basal plane has been passed along the trigonal C3 axis. Below the temperature of magnetic moment ordering...

The neutrally charged silicon-vacancy defect (SiV ⁰ ) is a colour centre in diamond with spin S = 1, a zero-phonon line (ZPL) at 946 nm and long spin coherence, which makes it a promising candidate for quantum network applications. For the proper performance of such colour centres, all of them must have identical optical characteristics. However, i...

We report the growth of Ge-doped homoepitaxial diamond films by microwave plasma CVD in GeH4-CH4-H2 gas mixtures at moderate pressures (70-100 Torr). Optical emission spectroscopy was used to monitor Ge, H, and C2 species in the plasma at different process parameters, and trends for intensities of those radicals, gas temperature, and excitation tem...

Flavins such as flavin mononucleotide or flavin adenine dinucleotide are bound by diverse proteins, yet have very similar spectra when in the oxidized state. Recently, we developed new variants of flavin-binding protein CagFbFP exhibiting notable blue (Q148V) or red (I52V A85Q) shifts of fluorescence emission maxima. Here, we use time-resolved and...

Bismuth-germanate glasses, which are well known as a promising active medium for broadband near-infrared spectral range fiber lasers and as an initial matrix for nonlinear optical glass ceramics, have been synthesized in a 5–50 mol% Bi2O3 wide concentration range. Their structural and physical characteristics were studied by Raman and FT-IR spectro...

Germanium-Vacancy (Ge-V) color centers in diamond have narrow-band photoluminescence (PL) at room temperature (RT) and attract considerable attention due to their possible application in quantum information technologies, biomedicine, and local optical thermometry. In this work, we used microwave plasma chemical vapor deposition (MPCVD) to synthesiz...

The change in the absorption spectra due to reversal of the direction of light propagation (nonreciprocity of absorption) is a consequence of a simultaneous violation of both time-reversal and spatial-inversion symmetries. Here, we report on a high-resolution spectroscopic study of absorption nonreciprocity in the noncentrosymmetric multiferroic Cu...

In this work, isothermal sections of the Ln2O3–Cr2O3–B2O3 (Ln = Gd–Lu) ternary oxide systems at 900, 1000, and 1100 °C were constructed by determining the phase relations by using a powder X-ray diffraction technique. As a result, these systems were divided into subsidiary subsystems. Two types of double borates, LnCr3(BO3)4 (Ln = Gd–Er) and LnCr(B...

Direct laser writing/ultra-hyperdoping technology was harnessed to fabricate a universal CMOS-compatible Si-based broadband (UV-THz) n-p junction detector, with its spectral response controlled by external liquid helium-nitrogen cooling. Near-far IR (2-40 μm) temperature-dependent photoconductivity (PC) was revealed in a biased n-p junction, made o...

Thermal conductivity [Formula: see text] of single-crystal CVD diamond lightly doped (about 3 ppm) with nitrogen has been measured at temperatures from 5.7 to 410 K. The sample was carefully characterized by optical absorption and photoluminescence spectroscopy for the presence of impurities. Nine different optically active defects related with nit...

Citation: Molchanova, A.; Boldyrev, K.; Kuzmin, N.; Veligzhanin, A.; Khaydukov, K.; Khaydukov, E.; Kondratev, O.; Gudim, I.; Mikliaeva, E.; Popova, M. Manganese Luminescent Centers of Different Valence in Yttrium Aluminum Borate Crystals. Materials 2023, 16, 537. Abstract: We present an extensive study of the luminescence characteristics of Mn impu...

The results of experimental and theoretical studies of the low-frequency region of infrared spectra and Raman scattering spectra in liquid cyclic hydrocarbons (arenes) and their halogen-substituted ones are analyzed. The results of experimental studies of 13 liquids in the range 20–700 cm–1 using a high-resolution all-wavelength vacuum Fourier spec...

Concentration series of single-phase SrF2:Eu solid solutions with a particle size of ≈50 nm were synthesized by precipitation from aqueous solutions. The bands of europium in the di- and trivalent states as well as a band of intrinsic exciton luminescence of strontium fluoride were identified in the X-ray luminescence spectra. The most intense lumi...

The spectral and kinetic characteristics of Er3+ ions in heavily doped BaY1.8Lu0.2F8 mixed crystals have been studied. Absorption and luminescence spectra were recorded for BaY1.8Lu0.2F8 crystals with Er3+ ion concentrations of 20.0 and 30.0 at.%. The kinetic dependences of luminescence decay in the infrared range have also been studied. A model of...

Upon the UV light irradiation of single-crystal diamonds doped with phosphorus, several effects have been observed. The integral intensity of phosphorus lines in FTIR absorption spectra under UV radiation was increased. A saturation effect depending on the power of the laser radiation was demonstrated. Narrowing of the phosphorus lines, as well as...

A concentration series of Y3Al5O12:Ce solid solutions were prepared, and the composition demonstrating the highest X-ray luminescence intensity of cerium was identified. Based on the best composition, a series of luminescent diamond–Y3Al5O12:Ce composite films were synthesized using microwave plasma-assisted chemical vapor deposition (CVD) in metha...

This work is focused on the investigation of the X‐ray’s interaction with the color centers in diamond. X‐rays have the high penetrating power of radiation, which allows performing unhindered modifications deeply in the bulk of diamond crystals. Here, we show that X‐rays irradiation of diamond can change the charge states of its defects, including...

On the basis of the high-resolution low-temperature photoluminescence spectra of LiYF4:Ho crystals we discuss spectral manifestations of disorder caused by random distribution of either the lithium isotopes or defects in the crystal lattice. A peculiar discrete spectral structure of a different nature was found in the magnetic-field-dependent spect...

Comprehensive spectroscopic, magnetization and theoretical studies of LaAlO3:Tm³⁺ single crystal in the ferroelastic R3¯c phase are reported. The Tm³⁺ ions substitute for the La³⁺ ions at sites with the D3 symmetry. High-resolution absorption, photoluminescence and site-selective emission and excitation spectra were measured in the broad spectral r...

We report high-resolution infrared Zeeman spectra in the region of transitions between electronic singlets in the ground ⁵I8 and the first excited ⁵I7 crystal-field manifolds of Ho³⁺ in ⁷LiYF4 in a magnetic field directed along the tetragonal c axis of the crystal. Well-resolved hyperfine structure exhibiting non-linear Zeeman hyperfine splittings...

The vibrational behaviour of the germanium-vacancy (GeV) in diamond is studied through its photoluminescence spectrum and first-principles modelled partial phonon density of states. The former is measured in a region below 600 cm⁻¹. The latter is calculated for the GeV center in its neutral, charged, and excited state. The photoluminescence spectru...

We analyze the field-dependent intensities of the coupled electron-phonon modes observed in the low-temperature far-infrared (terahertz) reflection spectra of PrFe3(BO3)4 and develop a theory based on the Green’s function approach. An excellent agreement between the experimental and theoretical data is achieved. The developed theory of the intensit...

Powders of single-phase solid solutions based on cerium-doped gadolinium-scandium-aluminum garnet were synthesized by coprecipitation from aqueous solutions followed by annealing at 1600 °C. The solubility limit of cerium in gadolinium-scandium-aluminum garnet was determined by X-ray powder diffraction and scanning electron microscopy. It has been...

We have studied spectral evolution of the $E_u^1$ phonon line of a topological insulator Bi$_{2-x}$Sr$_x$Se$_3$ with temperature. Unlike the Raman-active phonons, the $E_u^1$ mode demonstrates softening upon cooling the crystal, and the corresponding spectral line acquires a pronounced Fano-like shape at temperatures $T\lesssim100$ K. We interpret...

This work presents information on the growth and spectroscopic study of single crystals of copper metaborate doped with nickel Cu1-xNixB2O4 (x = 0.05, 0.1). In the absorption spectra of both crystals, satellites related to Cu centers distorted by impurity Ni atoms were observed near the lines of zero phonon transitions. Polarization studies in the...

The paper presents the transmission spectra of hybrid perovskite MAPbI3 single crystals near the fundamental absorption edge in a wide temperature range. The absorption coefficient α of the single crystal samples is estimated at a temperature T = 150 K for the light with a photon energy E = 1.6 eV and at T = 40 K for E = 1.8 eV. The obtained values...

The paper presents a flux crystal growth technique, studies of the structural peculiarities and the optical absorption spectra of double orthoborate TbCr3(BO3)4 with a huntite structure. The intensities of the phonon modes were used to determine the ratios of the rhombohedral and monoclinic polytypes for this compound, depending on the growth condi...

This work presents information on the growth and spectroscopic study of single crystals of copper metaborate doped with nickel Cu 1−x Nix B 2 O 4 (x = 0.05, 0.1). In the absorption spectra of both crystals, satellites related to Cu centers distorted by impurity Ni atoms were observed near the lines of zero phonon transitions. Polarization studies i...

The paper presents the transmission spectra of hybrid perovskite MAPbI 3 single crystals near the fundamental absorption edge in a wide temperature range. The absorption coefficient α of the single crystal samples is estimated at a temperature T = 150 K for the light with a photon energy E = 1.6 eV and at T = 40 K for E = 1.8 eV. The obtained value...

The paper presents a flux crystal growth technique, studies of the structural peculiarities and the optical absorption spectra of double orthoborate TbCr 3 (BO 3) 4 with a huntite structure. The intensities of the phonon modes were used to determine the ratios of the rhombohedral and monoclinic polytypes for this compound, depending on the growth c...

We measured the heat capacity, magnetic susceptibility, magnetization, magnetoelectric effect, and optical spectra of samarium chromium borate crystals. It was found that, in SmCr3(BO3)4 single crystals, structures with the space groups R32 and C2/c may coexist. Magnetic phase transitions were discovered at temperatures TN1=7.8±0.5K, TN2=6.7±0.5K,...

Inorganic metal halide perovskites are promising materials for next-generation technologies due to plethora of unique physical properties many of which cannot be observed in the oxide perovskites. On the other hand, the search for ferroelectricity and multiferroicity in lead-free inorganic halide perovskites remains a challenging research topic. He...

Inorganic metal halide perovskites are promising materials for next-generation technologies due to a plethora of unique physical properties, many of which cannot be observed in the oxide perovskites. On the other hand, the search for ferroelectricity and multiferroicity in lead-free inorganic halide perovskites remains a challenging research topic....

Silicon p-n junction photoelement fabricated on a p-doped wafer by sulfur-based n-doping of its sub-micron thick surface layer, exhibits at liquid-helium temperatures impurity-based near-far IR (2–21 $\mathrm{\mu}$ μ m) photoconductivity spectra in the form of well-resolved separate bands of neutral and ionized atomic-like and cluster-like sulfur c...

A detailed study of the structural phase transition in Eu1–xLaxFe3(BO3)4 mixed crystals as a function of composition is reported. By analyzing a frequency shift of an electronic f-f transition in high-resolution optical spectra of Eu3+ ions, we detected a decrease in the phase transition temperature Ts from 87.05 to 12.2 K (upon cooling) and a simu...

Гибридные металлорганические перовскиты (МОП) относятся к классу полупроводниковых материалов, применяемых при создании оптоэлектронных устройств. В однокомпонентных солнечных элементах на основе МОП в апреле 2021 года была достигнута 25,6% эффективность преобразования солнечной энергии в электрическую [1]. Рекордные показатели однокомпонентных сол...

The hydrothermal synthesis and characterization of 10%Yb3+:LiLuF4 (LLF) microcrystals are reported. A combination of X‐ray diffraction (XRD) analysis, analytical transmission electron microscopy (TEM), scanning TEM (STEM), energy‐dispersive X‐ray (EDX) spectroscopy), temperature‐dependent Fourier‐transform infrared (FTIR) spectroscopy, and photolum...

The crystal formation of CuB2O4:Ni in the fluxes based on the Li2WO4 - Bi2O3 - WO3 solvent has been studied. The crystallizing phases have been studied in dependence on WO3...

High-resolution spectroscopic studies of LaAlO3 single crystal doped with holmium ions are reported. Polarized and unpolarized absorption and luminescence spectra were measured in the broad spectral range from 2000 to 23000cm–1 at temperatures of 4.5–5 K. Additional measurements were fulfilled using site-selective laser spectroscopy. Energies and s...

A series of centrosymmetric and acentric whitlockite-type stoichiometric phosphates Ca8MEr(PO4)7, M = Ca²⁺, Mg²⁺, Zn²⁺ and Ca9-xZnxLa0.9(PO4)7:0.1Er³⁺ were synthesized through the high-temperature solid state route. The obtained phases were studied by a combination of methods including Synchrotron powder X-ray diffraction, dielectric spectroscopy,...

Multifunctional Pr³⁺:YPO4 single crystals were investigated by high-resolution optical Fourier spectroscopy. The analysis of the transmission and luminescence spectra allowed us to supplement information on crystal-field levels of the Pr³⁺ ion. Shapes of spectral lines corresponding to transitions from the ground state to the degenerated Γ5 crystal...

Transition metal oxyborates M3(BO3)2 (M = Mn, Co, Ni) belong to a group of materials with the kotoite structure and many of them demonstrate complex magnetic behavior as a result of competing interactions between magnetic ions in nonequivalent crystallographic positions. In this paper, we report results of the detailed infrared and Raman spectrosco...

Optical studies of NdxGd1-xCr3(BO3)4 0.01≤x≤1 crystals have been carried out. A significant concentration effect of the Nd3+ ion on the crystal structure of these solid solutions was identified. It was found from the absorption spectra of neodymium ions in the 4I9/2→11F3/2 transition region that at a concentration x>0.6 two nonequivalent Nd3+ cente...

The high-resolution terahertz reflection and mid- and near-infrared transmission spectroscopic studies of CH3NH3PbI3 hybrid perovskite single crystals are performed for the temperature range from 5 to 350 K. The observation of the torsional mode of the molecular cation (at 306 cm-1) and of 12 other low-frequency modes not observed before is reporte...

The kinetics of the electronic transitions within the f-shell of Dy³⁺ ions were studied with monitoring near- and mid-IR luminescence decay under pulsed laser excitation at 1.3 µm. The luminescence decay curves were found to be profoundly non-exponential in all bands in the range between 1.3-5.5 µm. Such behavior is attributed to cross-relaxation a...

The electronic band structure of the phosphorus-doped high-quality high-pressure and high-temperature-grown single crystal diamond was studied by infrared absorption, magneto-and electron paramagnetic resonance spectroscopy, and first-principles calculations. The complete picture of the 1s → np± and 1s → np0 (n = 2, 3, 4) donor transitions with new...

We have studied high-resolution low-temperature IR luminescence and absorption spectra of undoped high-quality SiC single crystals of the 4H and 6H hexagonal modifications. Narrow lines with a width of smaller than 0.2 cm-1 have been revealed, with some of which being observed for the first time. We have found that some of the lines in the 4H and 6...

We have studied and optimized conditions for spontaneous flux growth of TbCr3(BO3)4 crystals. Phase relations in the pseudoternary system TbCr3(BO3)4–K2Mo3O10–B2O3 have been studied in the temperature range 900–1130°C and the single-phase terbium chromium borate crystallization field has been mapped out. It has been shown that increasing the TbCr3(...