Leonid Kulik

Leonid Kulik
Russian Academy of Sciences | RAS · Institute of Solid State Physics

PhD, doctor of phys.-math. sciences, Professor of Rassian Academy of Science

About

123
Publications
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1,103
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Introduction
Skills and Expertise
Additional affiliations
January 1990 - present
Institute of Solid State Physics (ISSP) Russian Academy of Sciences
Position
  • Leading Researcher, Professor of Russian Academy of Sciences

Publications

Publications (123)
Article
Full-text available
Two-dimensional electron systems in a quantizing magnetic field are regarded as of exceptional interest, considering the possible role of anyons—quasiparticles with non-boson and non-fermion statistics—in applied physics. To this day, essentially none but the fractional states of the quantum Hall effect (FQHE) have been experimentally realized as a...
Article
Full-text available
A novel experimental optical method, based on photoluminescence and photo-induced resonant reflection techniques, is used to investigate the spin transport over long distances in a new, recently discovered collective state—magnetofermionic condensate. The given Bose–Einstein condensate exists in a purely fermionic system (ν = 2 quantum Hall insulat...
Preprint
Full-text available
Two-dimensional electron systems in a quantizing magnetic field are regarded as of exceptional interest, considering the possible role of anyons – quasiparticles with non-boson and non-fermion statistics – in applied physics. To this day, essentially none but the fractional states of the quantum Hall effect (FQHE) have been experimentally realized...
Article
Full-text available
Robust electrode materials without the addition of binders allow increasing efficiency of electrical storage devices. We demonstrate the fabrication of binder-free electrodes from modified single-walled carbon nanotubes (SWCNTs) for electrochemical double-layer capacitors (EDLCs). Modification of SWCNTs included a sonication in 1,2-dichlorobenzene...
Article
The spin coherence of two-dimensional electrons is determined by two independent mechanisms: a single particle relaxation owing to spatially fluctuating magnetic field, and a many-particle exchange interaction maintaining collective precession of the electron spins with a common Larmor frequency. In this study, we investigate the structure of a tim...
Article
Resonant and nonresonant photoluminescence spectra of a two-dimensional electron system have been studied under the conditions of the formation of the 1/3 fractional quantum Hall effect state. It has been shown that resonant photoluminescence, in contrast to nonresonant photoluminescence, is a universal marker of the formation of the 1/3 state in t...
Article
Full-text available
We studied neutral excitations in a two-dimensional electron gas with an orbital momentum ΔM=1 and spin projection over the magnetic field axis ΔSz=1 in the vicinity of a filling factor of 3/2. It is shown that the 3/2 state is a singular point in the filling factor dependence of the spin ordering of the two-dimensional electron gas. In the vicinit...
Article
Full-text available
An experimental technique based on time-resolved Kerr rotation allows a comparison of the spin stiffnesses of different spin-polarized and depolarized states in a two-dimensional electron system. With this technique, a new spin-correlated phase that has no known analogues was discovered. The new spin-depolarized phase is characterized by high spin...
Article
The recent experimental studies of extremely long-lived macroscopic ensembles of spin-cyclotron excitons (magnetoexcitons) which have to obey the Bose-Einstein statistics signal the emergence of an excitonic coherent phase. In the present paper the theory of a weakly interacting Bose gas of spin-cyclotron excitations is developed in terms of a viri...
Preprint
Full-text available
We studied neutral excitations in a two-dimensional electron system with an orbital momentum $\Delta M = 1$ and spin projection over magnetic field axis $\Delta S_z = 1$ in the vicinity of a filling factor of 3/2. It is shown that the 3/2 state is a singular point in the filling factor dependence of the spin ordering of the two-dimensional electron...
Article
Full-text available
In a dilute gas of triplet magnetoexcitons, complete thermalization does not occur because the energy and momentum cannot be conserved simultaneously. Relaxation to the lowest energy state becomes possible owing to exciton—exciton scattering upon reaching a certain critical exciton density. Since thermalization times are extremely large, ensembles...
Article
Experimental results on the properties of a recently discovered new collective state, the magnetofermionic condensate, are summarized herein. Condensation occurs in a fermionic system, a quantum Hall insulator (filling factor ν = 2), as a result of the formation of a dense ensemble of long‐lived spin cyclotron magnetoexcitons, composite bosons. At...
Article
Relaxation of nuclear spins located in the vicinity of 2D electron system confined in a 16 nm [001] AlAs/AlGaAs quantum well was studied with the aid of electron spin resonance (ESR) in the regime of integer and fractional quantum Hall effect. Nuclear spin-lattice relaxation time τ was measured from the time decay of the Overhauser shift near diffe...
Article
Full-text available
Magneto-fermionic condensate under study is a Bose-Einstein condensate of cyclotron spin-flip magnetoexcitons in a quantum Hall insulator. This condensate features unique properties such as millisecond range lifetime and hundreds of micrometers of propagation length. In this study, utilizing the photo-induced resonant reflection technique, we measu...
Article
Three-particle complexes consisting of two holes in the completely filled zero-electron Landau level and an excited electron in the unoccupied first Landau level are investigated in a quantum Hall insulator. The distinctive features of these three-particle complexes are an electron-hole mass symmetry and the small energy gap of the quantum Hall ins...
Article
Full-text available
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Article
The spin polarization features of an electron system and the relaxation of nonequilibrium spin excitations near an even-denominator fractional state of 3/2 in a two-dimensional electron system based on the GaAs/AlGaAs heterostructure are experimentally investigated. It is shown that the 3/2 state is a singular point in the filling factor dependence...
Preprint
Full-text available
Three-particle complexes consisting of two holes in the completely filled zero electron Landau level and an excited electron in the unoccupied first Landau level are investigated in a quantum Hall insulator. The distinctive features of these three-particle complexes are an electron-hole mass symmetry and the small energy gap of the quantum Hall ins...
Article
A fundamentally new collective state, namely, the magnetofermionic condensate, is discovered during photoexcitation of a sufficiently dense gas of long-lived triplet cyclotron magnetoexcitons in a twodimensional Hall insulator with a high electron mobility, a filling factor of ν = 2, and temperatures of T < 1 K. The condensed phase coherently inter...
Article
Full-text available
We report on optical visualization of spin propagation more than 100 µm. We present an electronic system in a new state of aggregation, the magnetofermionic condensate, in which the lowest-energy spin excitations - photoexcited spin-triplet magnetoexcitons - freely propagate over long distances, in the order of a millimeter, which implies non-diffu...
Article
Full-text available
Excitation of long-lived triplet magnetoexcitons in a Hall insulator (filling factor ν = 2) with a high mobility of electrons, at low temperatures, Т < 1 K, enabled to discover a new collective state − magnetofermionic condensate, that interacts coherently with an external electromagnetic field, exhibits superradiant properties and, owing to its lo...
Article
New lines are observed in the photoluminescence spectrum of a two-dimensional electron gas in a quantizing magnetic field at a filling factor of ν = 2 upon the photoexcitation of a nonequilibrium ensemble of cyclotron magnetoexcitons. Their energies lie in the region forbidden for single-particle optical transitions and allowed for inner transition...
Article
Full-text available
Excitation of long-lived triplet magnetoexcitons in a Hall insulator (filling factor ν = 2) with a high mobility of electrons, at low temperatures, Т < 1 K, enabled to discover a new collective state − magnetofermionic condensate , that interacts coherently with an external electromagnetic field, exhibits superradiant properties and, owing to its l...
Article
The possibility of creating dense ensembles of spin excitons, transferring them to macroscopic distances on the order of hundreds of microns, and recording the appearance of these excitons in the region spatially remote from the excitation point by means of simple techniques of photoexcitation and space-resolved detection of photoluminescence of a...
Article
A principally new collective state - magnetofer-mionic condensate - has been found at excitation of long-lived triplet cyclotron magnetoexcitons in Hall isolator with high electron mobility, filling factor ? = 2 and at low temperatures, ? < 1 ?. The condensed phase interacts coherently with external electromag-netic field, exhibiting super-emitting...
Article
The magnetic field dynamics of intersubband collective excitations in two-dimensional electron systems based on MgxZn1-xO/ZnO heterostructures is studied by the Raman scattering method. It is found that, upon the change in the spin polarization under conditions of the transition from the filling factor ν = 2 to ν = 1, the energy of the intersubband...
Article
The paper addresses the experimental technique that, when applied to a 2D-electron system in the integer quantum Hall regime with filling factor = 2 (the Hall insulating state), allows resonant excitation of magnetoexcitons, their detection, control of an ensemble of long-lived triplet excitons and investigation of their radiationless decay related...
Article
Full-text available
The coherent spin dynamics of a two-dimensional electron gas in a GaAs/AlGaAs quantum well is experimentally studied near the filling factors ν = 3 and 1. The nonmonotonic character of the dependence of the spin dephasing time of a Goldstone spin exciton on the filling factor is found experimentally. The observed effect can be due to the formation...
Article
Full-text available
Coherent condensate states of particles obeying either Bose or Fermi statistics are in the focus of interest in modern physics. Here we report on condensation of collective excitations with Bose statistics, cyclotron magnetoexcitons, in a high-mobility two-dimensional electron system in a magnetic field. At low temperatures, the dense non-equilibri...
Data
Supplementary Figures 1-3, Supplementary Note 1 and Supplementary References.
Article
An experimental technique is developed to perform photoexcitation of an ensemble of translationinvariant triplet excitons, to manipulate this ensemble, and to detect the properties of its components. In particular, the influence of temperature on the radiationless decay during the relaxation of an exciton spin into the ground state of a Hall insula...
Article
Full-text available
Experimental and theoretical studies of the coherent spin dynamics of two-dimensional GaAs/AlGaAs electron gas were performed. The system in the quantum Hall ferromagnet state exhibits a spin relaxation mechanism that is determined by many-particle Coulomb interactions. In addition to the spin exciton with changes in the spin quantum numbers of $\d...
Article
Full-text available
Resonant optical excitation was used to create a macroscopic nonequilibrium ensemble of “dark” excitons with an unprecedented long lifetime in a two-dimensional electron system placed in a quantizing magnetic field. Exotic three-particle and four-particle states, plasmarons and plasmon-exciton molecules, coupled with the surrounding electrons throu...
Article
Full-text available
An experimental technique for the indirect manipulation and detection of electron spins entangled in two-dimensional magnetoexcitons has been developed. The kinetics of the spin relaxation has been investigated. Photoexcited spin-magnetoexcitons were found to exhibit extremely slow relaxation in specific quantum Hall systems, fabricated in high mob...
Article
Experimental and theoretical research on neutral excitations in a two-dimensional electron gas in a strong magnetic field is reviewed. Methods for calculating excitation energies in the strong-field limit for integer and noninteger filling factors are considered. The effects of impurities and of the nonideality of the two-dimensional system on the...
Article
Resonance Rayleigh scattering of light by a two-dimensional electron system in the ultraquantum limit is investigated. The scattering process under study involves electronic states belonging to the two spin sublevels of the zero Landau level. It is shown that the main contribution to resonance Rayleigh scattering originates from the fluctuations of...
Article
Resonance reflection of light from a two-dimensional electron system in a strong magnetic field has been investigated in an ultraquantum limit. A line associated with the formation of a Laughlin liquid in the electron system has been discovered. Similar features have been observed in neither photoluminescence nor resonance Rayleigh scattering spect...
Article
Full-text available
Experimental and theoretical research on neutral excitations in a two-dimensional electron gas in a strong magnetic field is reviewed. Methods for calculating excitation energies in the strong-field limit for integer and noninteger filling factors are considered. The effects of impurities and of the nonideality of the two-dimensional system on the...
Article
Full-text available
Electron spin relaxation in a spin-polarized quantum Hall state is studied. Long spin relaxation times that are at least an order of magnitude longer than those measured in previous experiments were observed and explained within the spin-exciton relaxation formalism. Absence of any dependence of the spin relaxation time on the electron temperature...
Article
Resonance Rayleigh scattering of light by a two-dimensional electron system in the ultraquantum limit is investigated. The scattering process under study involves electronic states belonging to the two spin sublevels of the zero Landau level. It is shown that the main contribution to resonance Rayleigh scattering originates from the fluctuations of...
Article
Using the inelastic light scattering technique we observe the spin excitations for a quantum Hall ferromagnet with charged defects. The lowest energy spin excitation branch behaves as the theoretically predicted collective spin precession (“cyclotron”) mode of the spin-texture liquid. A coupling between the spin-exciton and the “cyclotron” mode ind...
Article
Full-text available
We investigated the resonant Rayleigh scattering in a two-dimensional electron system (2DES) and developed a differential technique for obtaining high-quality RRS spectra. Oscillations of the RRS scattering efficiency are observed. The oscillations are explained in terms of redistribution of electron spins within two spin subbands of the zero Landa...
Article
The excitation spectrum of a two-dimensional electron system in high-quality AlGaAs/GaAs quantum wells has been studied by Raman scattering. New Raman lines due to the excitation of interface D − complexes in which two electrons localized in a quantum well are coupled to a charged impurity at the quantum well interface have been identified. The gro...
Article
Full-text available
We report on the observation of a new spin mode in a quantum Hall system in the vicinity of odd electron filling factors under experimental conditions excluding the possibility of Skyrmion excitations. The new mode having presumably zero energy at odd filling factors emerges at small deviations from odd filling factors and couples to the spin-excit...
Article
One of the promising ways to perform single-photon counting of terahertz radiation consists in sensitive probing of plasma excitation in the electron gas upon photon absorption. We demonstrate the ultimate sensor operating on this principle. It is assembled from a GaAs/AlGaAs quantum dot, electron reservoir and superconducting single-electron trans...
Article
Full-text available
Inelastic light scattering spectroscopy discloses a novel type of cyclotron spin-flip excitation in a quantum Hall system around the nu = 1/3 filling. The excitation energy follows qualitatively the degree of electron spin polarization, reaching a maximum value at nu = 1/3. This characterizes the new excitation as a nu = 1/3 ferromagnet eigenmode....
Article
Full-text available
Inelastic light scattering spectroscopy around the \nu=1/3 filling discloses a novel type of cyclotron spin-flip excitation in a quantum Hall system in addition to the excitations previously studied. The excitation energy of the observed mode follows qualitatively the degree of electron spin polarization, reaching a maximum value at \nu=1/3 and thu...
Article
Full-text available
An antiphased magnetoplasma (MP) mode in a two-dimensional electron gas (2DEG) has been studied by means of inelastic light scattering (ILS) spectroscopy. Unlike the cophased MP mode it is purely quantum excitation which has no classic plasma analogue. It is found that zero momentum degeneracy for the antiphased and cophased modes predicted by the...
Article
We present an experimental study of a quantum dot for application to a single photon terahertz detector. A GaAs/AlGaAs quantum dot of ~1 micrometer size is defined by mesa patterning and metal gates. The charge polarization of the QD induced by the absorption of individual photons is detected by a metallic single electron transistor. We have invest...
Article
We introduce a terahertz radiation sensor in which the photon-induced ionization state of a quantum dot is monitored by a point contact formed in the same semiconductor heterostructure. For comparison we used a readout based on a single electron transistor coupled to the same quantum dot. The experiments prove functionality of the point contact-bas...
Article
The cyclotron excitation spectrum of selectively doped AlGaAs/GaAs quantum wells with a high (up to 2 × 107 cm2/(V s)) mobility of electrons has been studied by means of the Raman scattering. The lines of the Raman scattering by the excitations of D − complexes, the objects in which two electrons localized in a quantum well are coupled to a charged...
Article
Full-text available
We report on an inelastic light scattering study in the two-dimensional electron system at filling factor nu=1 . The energy and the inelastic cross section of the cyclotron spin-flip mode are analyzed. The exchange enhanced electronic g factor in the quantum Hall ferromagnet is measured. In addition to the magnetoplasmon and cyclotron spin-flip mod...
Article
Spin-polarized echo-detected electron paramagnetic resonance (EPR) spectra and the transversal relaxation rate T2(-1) of the photoexcited triplet state of fullerene C60 molecules were studied in o-terphenyl, 1-methylnaphthalene, and decalin glassy matrices. The model is composed of a fast (correlation time approximately 10(-12) s) pseudorotation of...
Article
Inelastic light scattering is used to study the spectra of neutral excitations and magnetoexcitations in single and double quantum wells. New excitation branches of charge, spin, and charge–spin densities are observed. It is shown that various electron and phonon excitation modes interact with one another to form hybrid modes. Exchange and correlat...
Article
Passive terahertz imaging of high spectral sensitivity can be performed using a low temperature sensor coupled to an optical system delivering radiation from room temperature. We study this system in application to security screening and material analysis. Different types of low temperature sensors based on GaAs/AlGaAs quantum dots have been design...
Article
We have developed a detector for photons in the terahertz region consisting of a lateral semiconductor quantum-dot (QD), defined in the two-dimensional electron gas (2-DEG) of a mesa-patterned heterostructure using three metallic gates, and a metallic single-electron transistor (SET) fabricated on top of the mesa. The SET is capacitively coupled to...