Double Electron–Electron Resonance Between Trapped Electron and Hole in a Semiconductor

We demonstrate the spin interactions between dispersedly trapped electrons and holes in a semiconductor using the double electron–electron resonance (DEER) method of the pulsed electron paramagnetic resonance (EPR) techniques. An aluminum-doped titanium dioxide crystal is adopted as a spin system, in which optically generated electrons and holes are trapped, to reveal EPR signals that appear close to each other at a selected crystal orientation under an external magnetic field. We used the four-pulse DEER method by applying two microwave frequencies to a microwave cavity for pumping electrons and probing holes at the optimum temperature of 32 K. The dipolar modulation in the probed signal by pumping interacting spins was successfully detected. The observed non-oscillating decay shape indicates that the detected interaction is caused by widely distributed trapped electron and hole spins over long distances. We were able to extract a spin-pair distribution function by the first derivative of a background-corrected curve, referring to a previously reported method.     

Anderson Localization in a Two-Dimensional Electron–Hole System

JETP Letters - Anderson localization is discovered in a highly disordered two-dimensional electron–hole system in a HgTe quantum well. The behavior of this localization is fundamentally...     

Terahertz Cyclotron Photoconductivity in a Highly Unbalanced Two-Dimensional Electron–Hole System

The magnetic properties of the α-Fe₂O₃ hematite at a high hydrostatic pressure have been studied by synchrotron Mössbauer spectroscopy (nuclear forward scattering (NFS)) on iron nuclei. Time-domain NFS spectra of hematite have been measured in a diamond anvil cell in the pressure range of 0–72 GPa and the temperature range of 36–300 K in order to study the magnetic properties at a phase transition near a critical pressure of ~50 GPa. In addition, Raman spectra at room temperature have been studied in the pressure range of 0–77 GPa. Neon has been used as a pressure-transmitting medium. The appearance of an intermediate electronic state has been revealed at a pressure of ~48 GPa. This state is probably related to the spin crossover in Fe³⁺ ions at their transition from the high-spin state (HS, S = 5/2) to a low-spin one (LS, S = 1/2). It has been found that the transient pressure range of the HS–LS crossover is extended from 48 to 55 GPa and is almost independent of the temperature. This surprising result differs fundamentally from other cases of the spin crossover in Fe³⁺ ions observed in other crystals based on iron oxides. The transition region of spin crossover appears because of thermal fluctuations between HS and LS states in the critical pressure range and is significantly narrowed at cooling because of the suppression of thermal excitations. The magnetic P–T phase diagram of α-Fe₂O₃ at high pressures and low temperatures in the spin crossover region has been constructed according to the results of measurements.     

Fermi Surface of a Quasi–Two-Dimensional Electron Gas

A model of the energy state of a quasi–two-dimensional electron gas is constructed based on a rectangular potential well of finite depth. The form of the Fermi surface and the character of its transformation from the true two-dimensional gas to the three-dimensional one are determined.     

On the Acid–Base State of the Surface of Semiconductor Components of the ZnSe–CdS System Exposed to Different Media

Using the methods of hydrolytic adsorption, mechanochemistry, and nonaqueous conductometric titration, the acid–base properties of the surfaces of binary semiconductors and solid solutions of the ZnSe?CdS system are studied. The nature of acid sites, and the extent, character, and mechanism of the surface (absorption) interaction are established. The interrelationships in the changes of the acid–base and bulk physical properties upon changing the chemical composition are determined, which make it possible to draw conclusions that are fundamentally important in scientific and practical aspects.     

Unoccupied Electron States and the Formation of Interface between Films of Dimethyl-Substituted Thiophene–Phenylene Coolygomers and Oxidized Silicon Surface

Physics of the Solid State - The unoccupied electron states and the boundary potential barrier during deposition of ultrathin films of dimethyl-substituted thiophene–phenylene coolygomers of...     

Trajectory Analysis in a Gyrotron Electron–Optical System with Allowance for the Cathode Surface Roughness

Radiophysics and Quantum Electronics - We propose a method for considering the spread of initial electron velocities caused by the roughness of the cathode surface while performing a...     

Photogalvanic Currents and Electrical Inhomogeneity of a 2D Structured Single Crystal of Ferroelectric–Semiconductor

Physics of the Solid State - The experiment, which makes it possible to clarify the mechanism of formation of electrical inhomogeneity of a TlGaSe2 crystal, is described. Evolution of the anomalous...     

Electron–Hole Dimers in the Parent Phase of Quasi–2D Cuprates

Physics of the Solid State - The key feature of parent cuprates of the La2CuO4 type, in addition to their high ionic polarizability and closeness to polarization catastrophe, is identified as their...     

Influence of the Diagonal and Off-Diagonal Electron–Phonon Interactions on the Formation of Local Polarons and Their Band Structure in Materials with Strong Electron Correlations

For systems with strong electron correlations and strong electron–phonon interaction, we analyze the electron–phonon interaction in local variables. The effects of the mutual influence of electron–electron and electron–phonon interactions that determine the structure of local Hubbard polarons are described. Using a system containing copper–oxygen layers as an example, we consider the competition between the diagonal and off-diagonal interactions of electrons with the breathing mode as the polaron band structure is formed within a corrected formulation of the polaron version of the generalized tight-binding method. The band structure of Hubbard polarons is shown to depend strongly on the temperature due to the excitation of Franck–Condon resonances. For an undoped La₂CuO₄ compound we have described the evolution of the band structure and the spectral function from the hole dispersion in an antiferromagnetic insulator at low temperatures with the valence band maximum at point (π/2, π/2) to the spectrum with the maximum at point (π, π) typical for the paramagnetic phase. The polaron line width at the valence band top and its temperature dependence agree qualitatively with angle-resolved photoemission spectroscopy for undoped cuprates.     

Surface Plasmon Polaritons in a Graphene–Semiconductor–Graphene Thin Film

Physics of the Solid State - Dispersion properties of surface plasmon polaritons in a semiconductor film with graphene plates in the far-IR range and the possibility of controlling propagation...     

Solid-Phase Interactions in the Bi–Au System

Physics of the Solid State - Contact solid-phase interactions under load in the Bi–Au binary system whose elements have significantly different rheological properties are studied. It was...     

Interactions in the Nitrobenzene–Molecular Sieves System

Implantation of nitrobenzene into the inner space of aluminosilicate mesoporous molecular sieves of the MSM–41 type was investigated. The interaction of nitrobenzene with the active centers of the inner surface of channels was studied by the method of IR spectroscopy. It was hypothesized that the possible mechanism of this interaction is the formation of hydrogen bonds of the –NO₂...HO–Al(Si) type.     

Coulomb Drag of Dipole Excitons in a Hybrid Exciton–Electron System

The effect of Coulomb drag on a gas of dipole excitons in spatially separated two-dimensional quantum wells containing electron and exciton gases is studied theoretically. The Coulomb drag of excitons can be used to control exciton transport in transistor structures whose active element is a two-dimensional gas of dipole excitons. Expressions for the exciton cross conductivity as a function of temperature are obtained for the diffusion and ballistic transport regimes. For each regime, the limiting cases in terms of the ratio of the Coulomb interaction screening length to the distance between the gases are analyzed. It is shown that, at temperatures exceeding considerably the exciton-gas degeneracy temperature, the cross conductivity is independent of the temperature, while in the opposite case it vanishes exponentially.     

High-Intensity-Laser–Matter Interactions: the Energy-Control System of the Pico Laser Facility

We consider the requirements of the energy-control system of the PICO laser facility and describe a design of the calorimeter based on the proposed method of laser-radiation-energy measurements using the calorimeter–sensor thermal response. We present the results of an experimental study of the calorimeter temporal parameters and dynamic analog memory.     

Observation of Phase Transitions in an Electron–Hole System Associated with Dislocation Cores in Cadmium Telluride

Bulletin of the Lebedev Physics Institute - Evolution of the fine structure of dislocation microphotoluminescence lines in cadmium telluride with a decrease in the optical-excitation power density...     

Electron–Phonon Renormalization of the Electron Mass in a Metal beyond the Adiabatic Approximation

Journal of Experimental and Theoretical Physics - We analyze the renormalization of the electron mass due to the electron–phonon interaction and interaction constant λ associated with...     

Self-Action Effects in the Propagation of Surface Magnetostatic Wave Pulses in a Magnonic Crystal–Dielectric–Metal Structure

Technical Physics - We have analyzed the self-action effects in the propagation of surface magnetostatic wave (SMSW) pulses in a 1D magnonic crystal–dielectric–metal structure in which...     

Brick Wall Model and the Spectrum of a Schwarzschild Black Hole

The quantum entropy of a scalar field near a Schwarzschild black hole is investigated by employing the brick-wall model in the grand canonical ensemble. A positive chemical potential is introduced if the cutoff is set to be of order of the Planck length. We also discuss the relation between the chemical potential and the mass quantum of the black hole.     

Thermally Stimulated Electron–Hole and Ionic Processes in Zinc Oxide Crystals

The principal results of the investigation of thermally stimulated electron–hole and ionic processes in hydrothermal and gas-phase ZnO single crystals preexcited at low temperatures, based on simultaneous study of photo-EPR and thermoluminescence (TL), are presented. The nature of the traps determining the TL peaks at 17, 24, 40, 53, 90–110, 140–150, and 160–200 K is discussed. In particular, it has been established that the lithium paramagnetic centers (Li_Zn ⁺–O^I) play the role of hole traps in ZnO giving green and red TL in the temperature range 160–200 K and, in the case of association with small-sized donors, also TL in the temperature range 90–110 K. The other traps are electronic in character, and in the presence of acceptor lithium in the crystals, they form yellow-orange TL. Optical quenching of TL has been evaluated, and it has been found that there is a difference E 0.75 eV between the thermal and optical energies of ionization of lithium acceptors. Irreversible ionic processes associated with the healing of cationic vacancies at T 360–420 K have been revealed.