This paper is devoted to the rare-earth borates described by the general formula RM3（BO3）4, M = Al, Fe, and Cr, that have non-centrosymmetric trigonal slructure of the natural mineral huntite. It give a brief review...This paper is devoted to the rare-earth borates described by the general formula RM3（BO3）4, M = Al, Fe, and Cr, that have non-centrosymmetric trigonal slructure of the natural mineral huntite. It give a brief review of a spectroscopic research on YbAI3（BO3）4 （YbAB）, on a large group of magnetic iron borates, and on NdCra（BO3）4.展开更多
Three examples were considered of the use of high resolution Fourier-transform optical spectroscopy for studying quality of rare-earth-doped crystals. The first example was connected with defects present in crystals g...Three examples were considered of the use of high resolution Fourier-transform optical spectroscopy for studying quality of rare-earth-doped crystals. The first example was connected with defects present in crystals grown by flux techniques. The second example dealt with detection of stresses and deformations in rare-earth-containing crystals, by registering splitting of spectral lines. The third example showed that a very small amount （at the level ofppm） of different RE ions present in a crystal could be determined using high-resolution spectroscopy. This work was carried out by the author＇s group in collaboration with several institutions in Rus- sia and abroad.展开更多
Highly active, stable and affordable surface enhanced Raman scattering （SERS） substrates were obtained by electrolyzing a mixture of AgNO3 （4 × 10^-4 mol/L） and Na3C6H5OTH2O （6 × 10^-5 mol/L） for 1, 2,...Highly active, stable and affordable surface enhanced Raman scattering （SERS） substrates were obtained by electrolyzing a mixture of AgNO3 （4 × 10^-4 mol/L） and Na3C6H5OTH2O （6 × 10^-5 mol/L） for 1, 2, 3 and 4 h at 7 V. With crystal violet （CV） as a test molecule, a portable Raman spectrometer with 785 nm laser excitation was employed to carry out the SERS detection. Colloidal Ag nanoparticles prepared by electrolyzing for 3 h with the particle size of （65 ±17） nm is a perfect SERS substrate for the ultratrace detection of CV, which displayed an enhancement factor of ca. 1.3 × 10^8 and the detection limit of CV is down to ca. 10-15 mol/L （ca. 10^-4 ppb） with 10^-1 mol/L KBr as aggregating agent. Thus, this SERS substrate will provide a hopeful foreground in ultratrace detection. Meanwhile, it will provide a possibility to bring Raman analysis out of the laboratory to process in situ, real-time detection and identification.展开更多
We report on the fast high-resohition study of LiLuF4：Tm3＋. The accurate energy level scheme of Tm3＋ in the LiLuF4 matrix was obtained for the 3H6.5.4, 3F4.3.2, and ^1G4 multiplets. It was shown that electric-dipol...We report on the fast high-resohition study of LiLuF4：Tm3＋. The accurate energy level scheme of Tm3＋ in the LiLuF4 matrix was obtained for the 3H6.5.4, 3F4.3.2, and ^1G4 multiplets. It was shown that electric-dipole transitions dominate for all the studied multiplets except the 3H5 one.展开更多
A current-driven source of long-range surface plasmons(LRSPs)on a duplex metal nanolayer is reported.Electrical excitation of LRSPs was experimentally observed in a planar structure,where an organic light-emitting fil...A current-driven source of long-range surface plasmons(LRSPs)on a duplex metal nanolayer is reported.Electrical excitation of LRSPs was experimentally observed in a planar structure,where an organic light-emitting film was sandwiched between two metal nanolayers that served as electrodes.To achieve the LRSP propagation in these metal nanolayers at the interface with air,the light-emitting structure was bordered by a one-dimensional photonic crystal(PC)on the other side.The dispersion of the light emitted by such a hybrid PC/organic-light-emitting-diode structure(PC/OLED)comprising two thin metal electrodes was obtained,with a clearly identified LRSP resonance peak.展开更多
We report on the crystal-field(CF)levels of Nd^3+in Nd3CrGe3Be2O14,a representative of recently synthesized Be-containing langasites.They are the first in the family to contain two magnetic subsystems,1 D chromium and...We report on the crystal-field(CF)levels of Nd^3+in Nd3CrGe3Be2O14,a representative of recently synthesized Be-containing langasites.They are the first in the family to contain two magnetic subsystems,1 D chromium and Kagome-like rare-earth ones.High-resolution broad-band temperature-dependent spectra allow us to find all five CF Kramers doublets of the ground 4I9/2 CF multiplet and 38 levels of the excited 4I11/2,13/2,15/2,4F3/2,4F5/2+2H9/2,4F7/2+4S3/2 and 4F9/2 CF multiplets.These data form a basis for a future exploration of this interesting two-sublattice magnet with frustrated interactions.Optical transitions between Kramers doublets of Nd^3+indicate magnetic activity of 1D-chromium chains at T<20 K.展开更多
We used the high-resolution spectroscopy to study the interactions that Tm3＋ ion in a LiYF4 crystal is subjected to. Several crystal field transitions with low integral intensity were found not registered before by m...We used the high-resolution spectroscopy to study the interactions that Tm3＋ ion in a LiYF4 crystal is subjected to. Several crystal field transitions with low integral intensity were found not registered before by means of ordinary spectroscopy. Spectral evidences for interionic, hyperfine, isotopic interactions, and for a resonant broadening of the ground state are presented.展开更多
Photolu min esce nee in clud ing fluoresce nee plays a great role in a wide variety of applicati ons from biomedical sensing and imag ing to optoelectr on ics.Therefore,the enhan ceme nt and con trol of photolu min es...Photolu min esce nee in clud ing fluoresce nee plays a great role in a wide variety of applicati ons from biomedical sensing and imag ing to optoelectr on ics.Therefore,the enhan ceme nt and con trol of photolu min esce nee has imme nse impact on both fun dame ntal scie ntific research and aforeme nti oned applicati ons.Among various nano phot tonic schemes and nanostructures to enhance the photoluminescence,we focus on a certain type of nanostructures,hyperbolic metamaterials(HMMs).HMMs are highly ani sotropic metamaterials,which produce intense localized electric fields.Therefore,HMMs n aturally boost photolu min esce nee from dye molecules,qua ntum dots,n itroge n-vaca ncy cen ters in diam on ds,perovskites and tra nsiti on metal dichalcoge nides.We provide an overview of various con figuratio ns of HMMs,i nclud ing metal-dielectric multilayers,trenches,metallic nanowires,and cavity structures fabricated with the use of noble metals,transparent conductive oxides,and refractory metals as plasmonic elements.We also discuss lasing action realized with HMMs.展开更多
Absorption spectra of the mixed chain nickelates （（NdxY1-x）2BaNiO5 were measured for different x. Experimentally two evidences for the presence of non-equivalent rare-earth centers （NEREC） were found. First, the ...Absorption spectra of the mixed chain nickelates （（NdxY1-x）2BaNiO5 were measured for different x. Experimentally two evidences for the presence of non-equivalent rare-earth centers （NEREC） were found. First, the linewidths show a very strong broadening for x when the calculated distribution over NEREC is wide. Second, a compficated lineshape of the lowest-frequency line in the region of the 4I9/2→4I1/2 electronic lransition is in good agreement with statistics of NEREC. A simple modeling for the line broadening due to NEREC is suggested.展开更多
Higher-order topological insulators(HOTIs)are unique materials hosting topologically protected states,whose dimensionality is at least by 2 lower than that of the bulk.Topological states in such insulators may be stro...Higher-order topological insulators(HOTIs)are unique materials hosting topologically protected states,whose dimensionality is at least by 2 lower than that of the bulk.Topological states in such insulators may be strongly confined in their corners which leads to considerable enhancement of nonlinear processes involving such states.However,all nonlinear HOTIs demonstrated so far were built on periodic bulk lattice materials.Here,we demonstrate the first nonlinear photonic HOTI with the fractal origin.Despite their fractional effective dimensionality,the HOTIs constructed here on two different types of the Sierpiński gasket waveguide arrays,may support topological corner states for unexpectedly wide range of coupling strengths,even in parameter regions where conventional HOTIs become trivial.We demonstrate thresholdless spatial solitons bifurcating from corner states in nonlinear fractal HOTIs and show that their localization can be efficiently controlled by the input beam power.We observe sharp differences in nonlinear light localization on outer and multiple inner corners and edges representative for these fractal materials.Our findings not only represent a new paradigm for nonlinear topological insulators,but also open new avenues for potential applications of fractal materials to control the light flow.展开更多
We consider a hybrid heterostructure containing an inorganic quantum well in close proximity with organic material as overlayer. The resonant optical pumping of Frenkel exciton can lead to an efficient indirect pumpin...We consider a hybrid heterostructure containing an inorganic quantum well in close proximity with organic material as overlayer. The resonant optical pumping of Frenkel exciton can lead to an efficient indirect pumping of Wannier excitons. As organic material in such a hybrid structure, we consider crystalline tetracene. In tetracene, the singlet exciton energy is close to twice the one of triplet exciton state and singlet exciton fission into two triplets can be efficient. This process in tetracene is thermally activated and we investigate here how the temperature-dependent exciton energy transfer affects the functional properties of hybrid organic-inorganic nanostructures. We have obtained the exact analytical solution of diffusion equation for organics at different temperatures defining different diffusion lengths of excitons. The effectiveness of energy transfer in hybrid with tetracene was calculated by definite method for two selected temperatures that open possibility to operate in full region of temperatures. Temperature dependence of energy transfer opens a new possibility to turn on and off the indirect pumping due to energy transfer from the organic subsystem to the inorganic subsystem.展开更多
For the past thirty years, intense efforts have been made to record atomic scale movies that reveal the movement of atoms in molecules, the fast dynamical processes in biological tissues and cells, and the changes in ...For the past thirty years, intense efforts have been made to record atomic scale movies that reveal the movement of atoms in molecules, the fast dynamical processes in biological tissues and cells, and the changes in the structure of a solid confined to nano-scale volumes. A combination of sub-nanometer spatial resolution with picosecond or even femtosecond temporal resolution is required for such atomic movies. Additional important information can be obtained when the energy of the electron beam transmitted through the sample is measured. The four dimensional (4D) spatially and temporally resolved ultrafast electron microscopy method is made possible by the extremely high detection efficiency that is reached in 4D electron microscopy. Using ultra-short electron bunches for the visualization of biological tissue can also improve the spatial resolution compared to conventional electron microscopes, thereby enabling the study of complex biological samples of relevance to the life sciences. Of particular interest to a broad audience is the possibility to create a video, and in the future, a real atomic movie, using 4D electron tomography.展开更多
With aim to increase set of modern commercial optoelectronic devices we investigate the optical properties of new triple semiconductor-organics-semiconductor nanostructure having two semiconductor layers with organic ...With aim to increase set of modern commercial optoelectronic devices we investigate the optical properties of new triple semiconductor-organics-semiconductor nanostructure having two semiconductor layers with organic layer between. This will be development to majority of modern publications with investigations of only double hybrid nanostructures with one contacting semiconductor layer and one organic layer. It is supposed that the energy of exciton in the first layer is larger than the energy of exciton in organic layer and that the energy of exciton in organic layer is larger in comparison with energy of exciton in second semiconductor layer. It was shown that installation of organics leads to some frequencies at different parameters or to reflection increasing and transmission decrease or to reverted dependence. New recurrent method of inverted calculation for fields is proposed and using this method the frequency dependences of optical characteristics have been calculated. The role of second semiconductor layer in considered triple structure has been estimated.展开更多
The open-air fabrication of quantum-dot light-emitting diodes(QLEDs)shows great potential for scalable manufacturing.However,the processing stability of QLED devices remains a fundamental barrier to their industrializ...The open-air fabrication of quantum-dot light-emitting diodes(QLEDs)shows great potential for scalable manufacturing.However,the processing stability of QLED devices remains a fundamental barrier to their industrialization.This study investigates the gas-related stability of QLEDs based on the ZnMgO electron transport layer(ETL).By analyzing the current density–voltage(J–V)characteristics of QLEDs and the corresponding sub-devices of functional layers in different gas environments,we demonstrate that the ZnMgO ETL plays a critical role in determining the gas-related stability of QLEDs.Further characterizations and density functional theory(DFT)calculations indicate that gas-induced surface reactions—particularly modifications to surface states and the formation of stable ZnMgO/OH—are the primary causes of performance degradation of QLEDs.展开更多
Creation of stable self-trapped vortex states(alias vortex solitons)in Bose-Einstein condensates(BECs)in free space is a challenging problem[1].To date,an experimental demonstration of this possibility is missing.A ne...Creation of stable self-trapped vortex states(alias vortex solitons)in Bose-Einstein condensates(BECs)in free space is a challenging problem[1].To date,an experimental demonstration of this possibility is missing.A new powerful platform for the realization of various self-trapped states is offered by quantum droplets(QDs),i.e.,stable localized modes maintained by the balance of mean-field(MF)interactions and corrections to them induced by quantum fluctuations[2].Recent theoretical predictions[3,4]and experimental demonstrations[5-10]suggest various possibilities for the creation of novel fundamental and vortical patterns,as summarized in reviews[11-13].In particular,QDs with embedded vorticity were theoretically investigated in detail[14-21].展开更多
Introduction of controllable deformations into periodic materials that lead to disclinations in their structure opens novel routes for construction of higher-order topological insulators hosting topological states at ...Introduction of controllable deformations into periodic materials that lead to disclinations in their structure opens novel routes for construction of higher-order topological insulators hosting topological states at disclinations.Appearance of these topological states is consistent with the bulk-disclination correspondence principle,and is due to the filling anomaly that results in fractional charges to the boundary unit cells.So far,topological disclination states were observed only in the linear regime,while the interplay between nonlinearity and topology in the systems with disclinations has been never studied experimentally.We report here on the experimental observation of the nonlinear photonic disclination states in waveguide arrays with pentagonal or heptagonal disclination cores inscribed in transparent optical medium using the fs-laser writing technique.The transition between nontopological and topological phases in such structures is controlled by the Kekulédistortion coefficient r with topological phase hosting simultaneously disclination states at the inner disclination core and spatially separated from them corner-I,corner-II,and extended edge states at the outer edge of the structure.We show that the robust nonlinear disclination states bifurcate from their linear counterparts and that location of their propagation constants in the gap and,hence,their spatial localization can be controlled by their power.Nonlinear disclination states can be efficiently excited by Gaussian input beams,but only if they are focused into the waveguides belonging to the disclination core,where such topological states reside.Our results open new prospects for investigation of nonlinear effects in topological systems with disclinations and are relevant for different areas of science,including Bose-Einstein and polariton condensates,where potentials with the disclinations can be created.展开更多
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 struc...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 LiYF4:Ho single crystals and the anticrossings of hyperfine levels in a magnetic field are demonstrated using a self-made setup based on a Bruker 125HR high-resolution Fourier spectrometer.This is the first observation of the resolved hyperfine structure and anticrossing hyperfine levels in the luminescence spectra of a crystal.The narrowest spectral linewidth is only 0.0022 cm-1.This fact together with a large value of the magnetic g factor of several crystal-field states creates prerequisites for developing magnetic field sensors,which can be in demand in modern quantum information technology devices operating at low temperatures.Very small random lattice strains characterizing the quality of a crystal can be detected using anticrossing points.展开更多
Comprehensive Summary SPASER nanoparticle(NP),with small size,ultranarrow spectral-line and good biocompatibility,is a potential biomedical nanoprobe.However,owning to the striking light absorption capacity of Au-reso...Comprehensive Summary SPASER nanoparticle(NP),with small size,ultranarrow spectral-line and good biocompatibility,is a potential biomedical nanoprobe.However,owning to the striking light absorption capacity of Au-resonator,huge energy could accumulate under strong pumping-laser,which would lead to poor photo-stability and unexpected photo-damage to SPASER NP,and is harmful to its future practical application but hasn't been systematically studied in experiment.展开更多
We developed a new single-layer atom chip with an additional U-shaped current-carrying structure.The new U-shaped microwire creates optimized magnetic field distribution,which increases the trapping volume of a magnet...We developed a new single-layer atom chip with an additional U-shaped current-carrying structure.The new U-shaped microwire creates optimized magnetic field distribution,which increases the trapping volume of a magneto-optical trap(MOT) near the chip.Our approach allows one to localize more atoms,while a setup remains relatively simple (single-layer approach) and consumes low current (up to 10 A). The total number of trapped^(87)Rb atoms in our setup is 5×10^(7).展开更多
Topological insulators are most frequently constructed using lattices with specific degeneracies in their linear spectra,such as Dirac points.For a broad class of lattices,such as honeycomb ones,these points and assoc...Topological insulators are most frequently constructed using lattices with specific degeneracies in their linear spectra,such as Dirac points.For a broad class of lattices,such as honeycomb ones,these points and associated Dirac cones generally appear in non-equivalent pairs.Simultaneous breakup of the time-reversal and inversion symmetry in systems based on such lattices may result in the formation of the unpaired Dirac cones in bulk spectrum,but the existence of topologically protected edge states in such structures remains an open problem.Here a photonic Floquet insulator on a honeycomb lattice with unpaired Dirac cones in its spectrum is introduced that can support unidirectional edge states appearing at the edge between two regions with opposite sublattice detuning.Topological properties of this system are characterized by the nonzero valley Chern number.Remarkably,edge states in this system can circumvent sharp corners without inter-valley scattering even though there is no total forbidden gap in the spectrum.Our results reveal unusual interplay between two different physical mechanisms of creation of topological edge states based on simultaneous breakup of different symmetries of the system.展开更多
基金supported in part by the Russian Foundation for Basic Research (07-02-01185)the Russian Academy of Sciences under thgrams for Basic Research
文摘This paper is devoted to the rare-earth borates described by the general formula RM3（BO3）4, M = Al, Fe, and Cr, that have non-centrosymmetric trigonal slructure of the natural mineral huntite. It give a brief review of a spectroscopic research on YbAI3（BO3）4 （YbAB）, on a large group of magnetic iron borates, and on NdCra（BO3）4.
基金Project supported in part by the Russian Foundation for Basic Research(13-02-01091)
文摘Three examples were considered of the use of high resolution Fourier-transform optical spectroscopy for studying quality of rare-earth-doped crystals. The first example was connected with defects present in crystals grown by flux techniques. The second example dealt with detection of stresses and deformations in rare-earth-containing crystals, by registering splitting of spectral lines. The third example showed that a very small amount （at the level ofppm） of different RE ions present in a crystal could be determined using high-resolution spectroscopy. This work was carried out by the author＇s group in collaboration with several institutions in Rus- sia and abroad.
基金supported by the National Natural Science Foundation of China(No.10864001)the Foundation of Science and Technology Department of Yunnan province(No.2005PY01-51)
文摘Highly active, stable and affordable surface enhanced Raman scattering （SERS） substrates were obtained by electrolyzing a mixture of AgNO3 （4 × 10^-4 mol/L） and Na3C6H5OTH2O （6 × 10^-5 mol/L） for 1, 2, 3 and 4 h at 7 V. With crystal violet （CV） as a test molecule, a portable Raman spectrometer with 785 nm laser excitation was employed to carry out the SERS detection. Colloidal Ag nanoparticles prepared by electrolyzing for 3 h with the particle size of （65 ±17） nm is a perfect SERS substrate for the ultratrace detection of CV, which displayed an enhancement factor of ca. 1.3 × 10^8 and the detection limit of CV is down to ca. 10-15 mol/L （ca. 10^-4 ppb） with 10^-1 mol/L KBr as aggregating agent. Thus, this SERS substrate will provide a hopeful foreground in ultratrace detection. Meanwhile, it will provide a possibility to bring Raman analysis out of the laboratory to process in situ, real-time detection and identification.
基金supported by the Russian Academy of Sciences under the grant of the Program "Quantum physics of condensed matter"the grant 09-02-01067-a of the Russian Foundation for Basic Research
文摘We report on the fast high-resohition study of LiLuF4：Tm3＋. The accurate energy level scheme of Tm3＋ in the LiLuF4 matrix was obtained for the 3H6.5.4, 3F4.3.2, and ^1G4 multiplets. It was shown that electric-dipole transitions dominate for all the studied multiplets except the 3H5 one.
基金supported by the Swiss National Science Foundation (Grant 200021_162767)
文摘A current-driven source of long-range surface plasmons(LRSPs)on a duplex metal nanolayer is reported.Electrical excitation of LRSPs was experimentally observed in a planar structure,where an organic light-emitting film was sandwiched between two metal nanolayers that served as electrodes.To achieve the LRSP propagation in these metal nanolayers at the interface with air,the light-emitting structure was bordered by a one-dimensional photonic crystal(PC)on the other side.The dispersion of the light emitted by such a hybrid PC/organic-light-emitting-diode structure(PC/OLED)comprising two thin metal electrodes was obtained,with a clearly identified LRSP resonance peak.
基金Project supported by the Russian Foundation for Basic Research(17-02-00603)
文摘We report on the crystal-field(CF)levels of Nd^3+in Nd3CrGe3Be2O14,a representative of recently synthesized Be-containing langasites.They are the first in the family to contain two magnetic subsystems,1 D chromium and Kagome-like rare-earth ones.High-resolution broad-band temperature-dependent spectra allow us to find all five CF Kramers doublets of the ground 4I9/2 CF multiplet and 38 levels of the excited 4I11/2,13/2,15/2,4F3/2,4F5/2+2H9/2,4F7/2+4S3/2 and 4F9/2 CF multiplets.These data form a basis for a future exploration of this interesting two-sublattice magnet with frustrated interactions.Optical transitions between Kramers doublets of Nd^3+indicate magnetic activity of 1D-chromium chains at T<20 K.
基金supported by the Russian Academy of Sciences under the grant 8.1 of the Program "Quantum macrophysics"the Russian Foundation for Basic Research
文摘We used the high-resolution spectroscopy to study the interactions that Tm3＋ ion in a LiYF4 crystal is subjected to. Several crystal field transitions with low integral intensity were found not registered before by means of ordinary spectroscopy. Spectral evidences for interionic, hyperfine, isotopic interactions, and for a resonant broadening of the ground state are presented.
基金L.Y.Beliaev,O.Takayama and A.V.Lavrinenko acknowledge the financial support from Independent Research Fund Denmark(DFF)(Research Project 2,8022-00387B)Denmark.PM acknowledges that the publication was prepared within the framework of Academic Fund Program at the HSE University in 2021(grant No 21-04-056).
文摘Photolu min esce nee in clud ing fluoresce nee plays a great role in a wide variety of applicati ons from biomedical sensing and imag ing to optoelectr on ics.Therefore,the enhan ceme nt and con trol of photolu min esce nee has imme nse impact on both fun dame ntal scie ntific research and aforeme nti oned applicati ons.Among various nano phot tonic schemes and nanostructures to enhance the photoluminescence,we focus on a certain type of nanostructures,hyperbolic metamaterials(HMMs).HMMs are highly ani sotropic metamaterials,which produce intense localized electric fields.Therefore,HMMs n aturally boost photolu min esce nee from dye molecules,qua ntum dots,n itroge n-vaca ncy cen ters in diam on ds,perovskites and tra nsiti on metal dichalcoge nides.We provide an overview of various con figuratio ns of HMMs,i nclud ing metal-dielectric multilayers,trenches,metallic nanowires,and cavity structures fabricated with the use of noble metals,transparent conductive oxides,and refractory metals as plasmonic elements.We also discuss lasing action realized with HMMs.
基金supported by the Russian Foundation for Basic Research (08-02-00690-a)the Russian Academy of Sciences under the Prograof Basic Research
文摘Absorption spectra of the mixed chain nickelates （（NdxY1-x）2BaNiO5 were measured for different x. Experimentally two evidences for the presence of non-equivalent rare-earth centers （NEREC） were found. First, the linewidths show a very strong broadening for x when the calculated distribution over NEREC is wide. Second, a compficated lineshape of the lowest-frequency line in the region of the 4I9/2→4I1/2 electronic lransition is in good agreement with statistics of NEREC. A simple modeling for the line broadening due to NEREC is suggested.
基金supported by the research project FFUU-2024-0003 of the Institute of Spectroscopy of the Russian Academy of Sciences and by the Russian Science Foundation(24-12-00167)funding by the Natural Science Basic Research Program of Shaanxi Province(2024JC-JCQN-06)+2 种基金the National Natural Science Foundation of China(12074308,12304370)the Fundamental Research Funds for the Central Universities(sxzy012024146)the Foundation for the Advancement of Theoretical Physics and Mathematics“BASIS”(22-2-2-26-1).
文摘Higher-order topological insulators(HOTIs)are unique materials hosting topologically protected states,whose dimensionality is at least by 2 lower than that of the bulk.Topological states in such insulators may be strongly confined in their corners which leads to considerable enhancement of nonlinear processes involving such states.However,all nonlinear HOTIs demonstrated so far were built on periodic bulk lattice materials.Here,we demonstrate the first nonlinear photonic HOTI with the fractal origin.Despite their fractional effective dimensionality,the HOTIs constructed here on two different types of the Sierpiński gasket waveguide arrays,may support topological corner states for unexpectedly wide range of coupling strengths,even in parameter regions where conventional HOTIs become trivial.We demonstrate thresholdless spatial solitons bifurcating from corner states in nonlinear fractal HOTIs and show that their localization can be efficiently controlled by the input beam power.We observe sharp differences in nonlinear light localization on outer and multiple inner corners and edges representative for these fractal materials.Our findings not only represent a new paradigm for nonlinear topological insulators,but also open new avenues for potential applications of fractal materials to control the light flow.
文摘We consider a hybrid heterostructure containing an inorganic quantum well in close proximity with organic material as overlayer. The resonant optical pumping of Frenkel exciton can lead to an efficient indirect pumping of Wannier excitons. As organic material in such a hybrid structure, we consider crystalline tetracene. In tetracene, the singlet exciton energy is close to twice the one of triplet exciton state and singlet exciton fission into two triplets can be efficient. This process in tetracene is thermally activated and we investigate here how the temperature-dependent exciton energy transfer affects the functional properties of hybrid organic-inorganic nanostructures. We have obtained the exact analytical solution of diffusion equation for organics at different temperatures defining different diffusion lengths of excitons. The effectiveness of energy transfer in hybrid with tetracene was calculated by definite method for two selected temperatures that open possibility to operate in full region of temperatures. Temperature dependence of energy transfer opens a new possibility to turn on and off the indirect pumping due to energy transfer from the organic subsystem to the inorganic subsystem.
文摘For the past thirty years, intense efforts have been made to record atomic scale movies that reveal the movement of atoms in molecules, the fast dynamical processes in biological tissues and cells, and the changes in the structure of a solid confined to nano-scale volumes. A combination of sub-nanometer spatial resolution with picosecond or even femtosecond temporal resolution is required for such atomic movies. Additional important information can be obtained when the energy of the electron beam transmitted through the sample is measured. The four dimensional (4D) spatially and temporally resolved ultrafast electron microscopy method is made possible by the extremely high detection efficiency that is reached in 4D electron microscopy. Using ultra-short electron bunches for the visualization of biological tissue can also improve the spatial resolution compared to conventional electron microscopes, thereby enabling the study of complex biological samples of relevance to the life sciences. Of particular interest to a broad audience is the possibility to create a video, and in the future, a real atomic movie, using 4D electron tomography.
文摘With aim to increase set of modern commercial optoelectronic devices we investigate the optical properties of new triple semiconductor-organics-semiconductor nanostructure having two semiconductor layers with organic layer between. This will be development to majority of modern publications with investigations of only double hybrid nanostructures with one contacting semiconductor layer and one organic layer. It is supposed that the energy of exciton in the first layer is larger than the energy of exciton in organic layer and that the energy of exciton in organic layer is larger in comparison with energy of exciton in second semiconductor layer. It was shown that installation of organics leads to some frequencies at different parameters or to reflection increasing and transmission decrease or to reverted dependence. New recurrent method of inverted calculation for fields is proposed and using this method the frequency dependences of optical characteristics have been calculated. The role of second semiconductor layer in considered triple structure has been estimated.
基金supported by grants from the National Natural Science Foundation of China(Nos.U23A20683 and 62301033)from the Ministry of Science and High Education of Russian Federation(Project No.FSRZ-2023-0006).
文摘The open-air fabrication of quantum-dot light-emitting diodes(QLEDs)shows great potential for scalable manufacturing.However,the processing stability of QLED devices remains a fundamental barrier to their industrialization.This study investigates the gas-related stability of QLEDs based on the ZnMgO electron transport layer(ETL).By analyzing the current density–voltage(J–V)characteristics of QLEDs and the corresponding sub-devices of functional layers in different gas environments,we demonstrate that the ZnMgO ETL plays a critical role in determining the gas-related stability of QLEDs.Further characterizations and density functional theory(DFT)calculations indicate that gas-induced surface reactions—particularly modifications to surface states and the formation of stable ZnMgO/OH—are the primary causes of performance degradation of QLEDs.
基金supported by the National Natural Science Foundation of China through Grant Nos.12274077,12475014,11874112,and 11905032the Natural Science Foundation of Guangdong Province through Grant Nos.2024A1515030131 and 2023A1515010770+2 种基金the Research Fund of Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology through Grant No.2020B1212030010supported,in part,by the Israel Science Foundation through Grant No.1695/2022research project FFUU-2024-0003 of the Institute of Spectroscopy of the Russian Academy of Sciences.
文摘Creation of stable self-trapped vortex states(alias vortex solitons)in Bose-Einstein condensates(BECs)in free space is a challenging problem[1].To date,an experimental demonstration of this possibility is missing.A new powerful platform for the realization of various self-trapped states is offered by quantum droplets(QDs),i.e.,stable localized modes maintained by the balance of mean-field(MF)interactions and corrections to them induced by quantum fluctuations[2].Recent theoretical predictions[3,4]and experimental demonstrations[5-10]suggest various possibilities for the creation of novel fundamental and vortical patterns,as summarized in reviews[11-13].In particular,QDs with embedded vorticity were theoretically investigated in detail[14-21].
基金B.R.,H.W.and Y.Z.acknowledge funding by the National Natural Science Foundation of China(Grant No.:12074308)the Fundamental Research Funds for the Central Universities(Grant No.:xzy022022058)+2 种基金A.A.A.,Y.V.K.,S.A.Z.,N.N.S.,A.A.K.,V.O.K.,S.V.C.,and V.N.Z.acknowledge funding by the Russian Science Foundation grant 21-12-00096the research project FFUU2021-0003 of the Institute of Spectroscopy of the Russian Academy of Sciences.A.A.KS.P.K.are supported by the Ministry of Science and Higher Education of the Russian Federation on the basis of the FSAEIHE SUSU(NRU)(Agreement No.:075-15-2022-1116).
文摘Introduction of controllable deformations into periodic materials that lead to disclinations in their structure opens novel routes for construction of higher-order topological insulators hosting topological states at disclinations.Appearance of these topological states is consistent with the bulk-disclination correspondence principle,and is due to the filling anomaly that results in fractional charges to the boundary unit cells.So far,topological disclination states were observed only in the linear regime,while the interplay between nonlinearity and topology in the systems with disclinations has been never studied experimentally.We report here on the experimental observation of the nonlinear photonic disclination states in waveguide arrays with pentagonal or heptagonal disclination cores inscribed in transparent optical medium using the fs-laser writing technique.The transition between nontopological and topological phases in such structures is controlled by the Kekulédistortion coefficient r with topological phase hosting simultaneously disclination states at the inner disclination core and spatially separated from them corner-I,corner-II,and extended edge states at the outer edge of the structure.We show that the robust nonlinear disclination states bifurcate from their linear counterparts and that location of their propagation constants in the gap and,hence,their spatial localization can be controlled by their power.Nonlinear disclination states can be efficiently excited by Gaussian input beams,but only if they are focused into the waveguides belonging to the disclination core,where such topological states reside.Our results open new prospects for investigation of nonlinear effects in topological systems with disclinations and are relevant for different areas of science,including Bose-Einstein and polariton condensates,where potentials with the disclinations can be created.
基金support from the Russian ScienceFoundation under Grant#19-72-10132.M.N.P.was supported by the Ministry of Science and Higher Education.of Russia(Grant 0039-2019-0004).
文摘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 LiYF4:Ho single crystals and the anticrossings of hyperfine levels in a magnetic field are demonstrated using a self-made setup based on a Bruker 125HR high-resolution Fourier spectrometer.This is the first observation of the resolved hyperfine structure and anticrossing hyperfine levels in the luminescence spectra of a crystal.The narrowest spectral linewidth is only 0.0022 cm-1.This fact together with a large value of the magnetic g factor of several crystal-field states creates prerequisites for developing magnetic field sensors,which can be in demand in modern quantum information technology devices operating at low temperatures.Very small random lattice strains characterizing the quality of a crystal can be detected using anticrossing points.
基金mainly supported by the National Natural Science Foundation of China(Nos.22174064,22034003)the Excellent Research Program of Nanjing University(No.ZYJH004)+1 种基金the State Key Laboratory of Analytical Chemistry for Life Science(No.5431ZZXM2002)the Program B for Outstanding Ph.D.
文摘Comprehensive Summary SPASER nanoparticle(NP),with small size,ultranarrow spectral-line and good biocompatibility,is a potential biomedical nanoprobe.However,owning to the striking light absorption capacity of Au-resonator,huge energy could accumulate under strong pumping-laser,which would lead to poor photo-stability and unexpected photo-damage to SPASER NP,and is harmful to its future practical application but hasn't been systematically studied in experiment.
基金supported by the Russian Science Foundation (No.23-22-00255)。
文摘We developed a new single-layer atom chip with an additional U-shaped current-carrying structure.The new U-shaped microwire creates optimized magnetic field distribution,which increases the trapping volume of a magneto-optical trap(MOT) near the chip.Our approach allows one to localize more atoms,while a setup remains relatively simple (single-layer approach) and consumes low current (up to 10 A). The total number of trapped^(87)Rb atoms in our setup is 5×10^(7).
基金Natural Science Basic Research Program of Shaanxi Province(2024JC-JCQN-06)National Natural Science Foundation of China(12074308,12304370)+1 种基金Fundamental Research Funds for the Central Universities(sxzy012024146)Research Project of the Institute of Spectroscopy of the Russian Academy of Sciences(FFUU-2024-0003)。
文摘Topological insulators are most frequently constructed using lattices with specific degeneracies in their linear spectra,such as Dirac points.For a broad class of lattices,such as honeycomb ones,these points and associated Dirac cones generally appear in non-equivalent pairs.Simultaneous breakup of the time-reversal and inversion symmetry in systems based on such lattices may result in the formation of the unpaired Dirac cones in bulk spectrum,but the existence of topologically protected edge states in such structures remains an open problem.Here a photonic Floquet insulator on a honeycomb lattice with unpaired Dirac cones in its spectrum is introduced that can support unidirectional edge states appearing at the edge between two regions with opposite sublattice detuning.Topological properties of this system are characterized by the nonzero valley Chern number.Remarkably,edge states in this system can circumvent sharp corners without inter-valley scattering even though there is no total forbidden gap in the spectrum.Our results reveal unusual interplay between two different physical mechanisms of creation of topological edge states based on simultaneous breakup of different symmetries of the system.
