arXiv subjects

V. V. Osipov

Publications and source records attributed to V. V. Osipov.

At least 19 recordsLinked to original sources

arXiv2011

Cavitation-induced ignition of cryogenic hydrogen-oxygen fluids

The Challenger disaster and purposeful experiments with liquid hydrogen (H2) and oxygen (Ox) tanks demonstrated that cryogenic H2/Ox fluids always self-ignite in the process of their mixing. Here we propose a cavitation-induced self-ignition mechanism that may be realized under these conditions. In one possible scenario, self-ignition is caused by the strong shock waves generated by the collapse of pure Ox vapor bubble near the surface of the Ox liquid that may initiate detonation of the gaseous H2/Ox mixture adjacent to the gas-liquid interface. This effect is further enhanced by H2/Ox combustion inside the collapsing bubble in the presence of admixed H2 gas.

physics.flu-dyn↗

arXiv2008

Bit storage by $360^\circ$ domain walls in ferromagnetic nanorings

We propose a design for the magnetic memory cell which allows an efficient storage, recording, and readout of information on the basis of thin film ferromagnetic nanorings. The information bit is represented by the polarity of a stable 360$^\circ$ domain wall introduced into the ring. Switching between the two magnetization states is achieved by the current applied to a wire passing through the ring, whereby the $360^\circ$ domain wall splits into two charged $180^\circ$ walls, which then move to the opposite extreme of the ring to recombine into a $360^\circ$ wall of the opposite polarity.

cond-mat.mtrl-sci↗

arXiv2008

Model based IVHM system for the solid rocket booster

We report progress in the development of a model-based hybrid probabilistic approach to an on-board IVHM for solid rocket boosters (SRBs) that can accommodate the abrupt changes of the model parameters in various nonlinear dynamical off-nominal regimes. The work is related to the ORION mission program. Specifically, a case breach fault for SRBs is considered that takes into account burning a hole through the rocket case, as well as ablation of the nozzle throat under the action of hot gas flow. A high-fidelity model (HFM) of the fault is developed in FLUENT in cylindrical symmetry. The results of the FLUENT simulations are shown to be in good agreement with quasi-stationary approximation and analytical solution of a system of one-dimensional partial differential equations (PDEs) for the gas flow in the combustion chamber and in the hole through the rocket case.

physics.data-an↗

arXiv2006

Complete spin polarization of degenerate electrons in semiconductors near ferromagnetic contacts

We show that spin polarization of electron density in nonmagnetic degenerate semiconductors can achieve 100%. This effect is realized in ferromagnet-semiconductor $FM-n^{+}$-$n$ junctions even at moderate spin selectivity of the $FM-n^{+}$ contact when the electrons are extracted from the heavily doped $n^{+}-$semiconductor into the ferromagnet. We derived a general equation relating spin polarization of the current to that of the electron density in nonmagnetic semiconductors. We found that the effect of the complete spin polarization is achieved near $n^{+}$-$n$ interface when an effective diffusion coefficient goes to zero in this region while the diffusion current remains finite.

cond-mat.other↗

arXiv2006

Electronic Control and Readout of Qubit States in Solid State Quantum Computing Systems

We demonstrate that an $n^+/i/n^+$ junction is the most suitable candidate for electronic control and readout of qubit states in quantum computing systems based on shallow impurities. The signature of this system is that the $n^+-$regions serve as metallic electrodes separated form the $i-$region by a self-induced barrier (internal workfunction). The $n^+/i/n^+$ system mimics the properties of a metal-vacuum-metal junction with the qubit (impurity atom) placed in a ``vacuum'' $i$-region between two ``metallic'' $n^+$ electrodes. We will show that the self-induced barrier exists in a sufficiently wide range of the concentration of dopants in the $n^+$-semiconductor (e.g. up to $10^{21}$ cm$^{-3}$ for Si) and its height can be controlled by tuning the doping level. A shallow donor placed in a vacuum $i$-region will be populated with one electron in equilibrium. In the case of Li donor in Si the $n^+$-electrodes will be used for a precision placement of the Li atom during the growth process; for voltage control and manipulation of the qubit states; and for a qubit readout by means of the optically stimulated resonant tunnelling. Another important feature of our system is that the qubit states (first two lowest energy levels of Li in Si) are separated by an energy gap from a continuum of the many-body states of the controlling electrodes.

cond-mat.other↗

arXiv2005

Complete spin extraction from semiconductors near ferromagnet-semiconductor interfaces

We show that spin polarization of electrons in nonmagnetic semiconductors near specially tailored ferromagnet-semiconductor junctions can achieve 100%. This effect is realized even at moderate spin injection coefficients of the contact when these coefficients only weakly depend on the current. The effect of complete spin extraction occurs at relatively strong electric fields and arises from a reduction of spin penetration length due to the drift of electrons from a semiconductor towards the spin-selective tunnel junction.

cond-mat.other↗

arXiv2005

Complete spin polarization of electrons in semiconductor layers and quantum dots

We demonstrate that non-equilibrium electrons in thin nonmagnetic semiconductor layers or quantum dots can be fully spin polarized by means of simultaneous electrical spin injection and extraction. The complete spin polarization is achieved if the thin layers or quantum dots are placed between two ferromagnetic metal contacts with moderate spin injection coefficients and antiparallel magnetizations. The sign of the spin polarization is determined by the direction of the current. Aplications of this effect in spintronics and quantum information processing are discussed.

cond-mat.other↗

arXiv2005

Spin accumulation in degenerate semiconductors near modified Schottky contact with ferromagnets

We study spin transport in forward and reverse biased junctions between a ferromagnetic metal and a degenerate semiconductor with a delta-doped layer near the interface at relatively low temperatures. We show that spin polarization of electrons in the semiconductor, Pn, near the interface increases both with the forward and reverse current and reaches saturation at certain relatively large current while the spin injection coefficient, Gamma, increases with reverse current and decreases with the forward current. We analyze the condition for efficient spin polarization of electrons in degenerate semiconductor near interface with ferromagnet. We compare the accumulation of spin polarized electrons in degenerate semiconductors at low temperatures with that in nondegenerate semiconductors at relatively high, room temperatures.

cond-mat.mtrl-sci↗

arXiv2004

Quantum computing on long-lived donor states of Li in Si

We predict a gigantically long lifetime of the first excited state of an interstitial lithium donor in silicon. The nature of this effect roots in the anomalous level structure of the {\em 1s} Li manifold under external stress. Namely, the coupling between the lowest two states of the opposite parity is very weak and occurs via intervalley phonon transitions only. We propose to use these states under the controlled ac and dc stress to process quantum information. We find an unusual form of the elastic-dipole interaction between %the electronic transitions in different donors. This interaction scales with the inter-donor distance $R$ as $R^{-3}$ or $R^{-5}$ for the transitions between the states of the same or opposite parity, respectively. The long-range $R^{-3}$ interaction provides a high fidelity mechanism for 2-qubit operations.

quant-ph↗

arXiv2004

Efficient nonlinear room-temperature spin injection from ferromagnets into semiconductors through a modified Schottky barrier

We suggest a consistent microscopic theory of spin injection from a ferromagnet (FM) into a semiconductor (S). It describes tunneling and emission of electrons through modified FM-S Schottky barrier with an ultrathin heavily doped interfacial S layer . We calculate nonlinear spin-selective properties of such a reverse-biased FM-S junction, its nonlinear I-V characteristic, current saturation, and spin accumulation in S. We show that the spin polarization of current, spin density, and penetration length increase with the total current until saturation. We find conditions for most efficient spin injection, which are opposite to the results of previous works, since the present theory suggests using a lightly doped resistive semiconductor. It is shown that the maximal spin polarizations of current and electrons (spin accumulation) can approach 100% at room temperatures and low current density in a nondegenerate high-resistance semiconductor.

cond-mat.mtrl-sci↗

arXiv2004

Highly polarized injection luminescence in forward-biased ferromagnetic-semiconductor junctions at low spin polarization of current

We consider electron tunneling from a nonmagnetic $n$-type semiconductor ($n$-S) into a ferromagnet (FM) through a very thin forward-biased Schottky barrier resulting in efficient extraction of electron spin from a thin $n$-S layer near FM-S interface at low spin polarization of the current. We show that this effect can be used for an efficient polarization radiation source in a heterostructure where the accumulated spin polarized electrons are injected from $n$-S and recombine with holes in a quantum well. The radiation polarization depends on a bias voltage applied to the FM-S junction.

cond-mat.mtrl-sci↗

arXiv2004

A class of spin injection-precession ultrafast nanodevices

Spin valve ultrafast spin injection devices are described: an amplifier, a frequency multiplier, and a square-law detector. Their operation is based on injection of spin polarized electrons from one ferromagnet to another through a semiconductor layer and spin precession of the electrons in the semiconductor layer in a magnetic field induced by a (base) current in an adjacent nanowire. The base current can control the emitter current between the magnetic layers with frequencies up to several 100 GHz.

cond-mat.mtrl-sci↗

arXiv2004

High-frequency spin valve effect in ferromagnet-semiconductor-ferromagnet structure based on precession of injected spins

New mechanism of magnetoresistance, based on tunneling-emission of spin polarized electrons from ferromagnets (FM) into semiconductors (S) and precession of electron spin in the semiconductor layer under external magnetic field, is described. The FM-S-FM structure is considered, which includes very thin heavily doped (delta-doped) layers at FM-S interfaces. At certain parameters the structure is highly sensitive at room-temperature to variations of the field with frequencies up to 100 GHz. The current oscillates with the field, and its relative amplitude is determined only by the spin polarizations of FM-S junctions at relatively large bias voltage.

cond-mat.mtrl-sci↗

arXiv2003

Spin extraction from a non-magnetic semiconductor

New efficient mechanism of obtaining spin polarization in_nonmagnetic_ semiconductors at arbitrary temperutures is described. The effect appears during tunneling of electrons from a nonmagnetic semiconductors (S) into ferromagnet (FM) through a Schottky barrier modified with very thin heavily doped interfacial layer. We show that electrons with a certain spin projection are extracted from S, while electrons with the opposite spins are accumulated in S. The spin density increases and spin penetration depth decreases with current.

cond-mat.mtrl-sci↗

arXiv2000

Symmetry breaking of vibrating interfaces: a mechanism for morphogenesis

We show that very small-amplitude oscillations of a highly symmetric, spheric or cylindrical, interface (thin membrane) between two fluids can result in inhomogeneous instability and breaking of the interface symmetry: the frequency of the breathing vibration selects the spatial symmetry. This mechanism may govern morphogenesis.

physics.flu-dyn↗

arXiv2000

Nature of Sonoluminescence: Noble Gas Radiation Excited by Hot Electrons in "Cold" Water

We show that strong electric fields occurring in water near the surface of collapsing gas bubbles because of the flexoelectric effect can provoke dynamic electric breakdown in a micron-size region near the bubble and consider the scenario of the SBSL. The scenario is: (i) at the last stage of incomplete collapse of the bubble the gradient of pressure in water near the bubble surface has such a value and sign that the electric field arising from the flexoelectric effect exceeds the threshold field of the dynamic electrical breakdown of water and is directed to the bubble center; (ii) mobile electrons are generated because of thermal ionization of water molecules near the bubble surface; (iii) these electrons are accelerated in ''cold'' water by the strong electric fields; (iv) these hot electrons transfer noble gas atoms dissolved in water to high-energy excited states and optical transitions between these states produce SBSL UV flashes in the trasparency window of water; (v) the breakdown can be repeated several times and the power and duration of the UV flash are determined by the multiplicity of the breakdowns. The SBSL spectrum is found to resemble a black-body spectrum where temperature is given by the effective temperature of the hot electrons. The pulse energy and some other characteristics of the SBSL are found to be in agreement with the experimental data when realistic estimations are made.

physics.flu-dyn↗

arXiv2000

Spike autosolitons in the Gray-Scott model

We performed a comprehensive study of the spike autosolitons: self-sustained solitary inhomogeneous states, in the classical reaction-diffusion system --- the Gray-Scott model. We developed singular perturbation techniques based on the strong separation of the length scales to construct asymptotically the solutions in the form of a one-dimensional static autosolitons, higher-dimensional radially-symmetric static autosolitons, and two types of traveling autosolitons. We studied the stability of the static autosolitons in one and three dimensions and analyzed the properties of the static and the traveling autosolitons.

patt-sol↗

arXiv1998

Theory of Spike Spiral Waves in a Reaction-Diffusion System

We discovered a new type of spiral wave solutions in reaction-diffusion systems --- spike spiral wave, which significantly differs from spiral waves observed in FitzHugh-Nagumo-type models. We present an asymptotic theory of these waves in Gray-Scott model. We derive the kinematic relations describing the shape of this spiral and find the dependence of its main parameters on the control parameters. The theory does not rely on the specific features of Gray-Scott model and thus is expected to be applicable to a broad range of reaction-diffusion systems.

patt-sol↗