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Top 20 Most Cited Articles
The 20 most cited articles over time based on CrossRef data.
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Peculiar physical properties and the colossal magnetoresistance of manganites (Review) Low Temp. Phys. 26, 171 (2000); http://dx.doi.org/10.1063/1.593890 (23 pages) | Cited 79 times
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An attempt is made to analyze the most important physical properties of manganites of the La-Ca-Mn-O type, which exhibit the colossal magnetoresistance effect. The primary focus is on the peculiarities of these compounds which are reflected in their crystalline, electronic, and magnetic structures and which determine the possible mechanisms by which an external magnetic field can exert a substantial influence on the transport characteristics of the current carriers in manganites. The combined effect of these factors is to create the necessary conditions for a metal-insulator phase transition that is sensitive to an external magnetic field. Another major topic in this review is a discussion of the scientific problems confronting the physics of manganites. © 2000 American Institute of Physics. |
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Formation and characterization of neutral krypton and xenon hydrides in low-temperature matrices Low Temp. Phys. 26, 680 (2000); http://dx.doi.org/10.1063/1.1312395 (11 pages) | Cited 55 times
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A family of rare-gas-containing hydrides HXY (where X=Kr or Xe, and Y is an electronegative fragment) is described. These molecules are experimentally prepared in low-temperature matrices by photodissociation of a hydrogen-containing HY precursor and thermal mobilization of the photodetached hydrogen atoms. The neutral HXY molecules are formed in a concerted reaction H+Y→HXY. Experimental evidence for the formation of these species is essentially based on strong infrared absorption bands that appear after annealing of the photolyzed matrices and are assigned to the H-X stretch of the HXY molecules. Computationally, the formation of these HXY molecules decreases the H-X distance by a factor of ⩾2 from its van der Waals value, which emphasizes their true chemical bonding, possessing both covalent and ionic contributions. The estimated dissociation energies vary from 0.4 to 1.4 eV and hold promise for forthcoming observation of these molecules in the gas phase. The experiments with the HXY molecules widen our knowledge on solid-state photolysis dynamics of hydrogen-containing species. In particular, the photolysis of small HY hydrides in solid Xe seems to be a quite local process, and the accompanying losses of H atoms play a minor role. © 2000 American Institute of Physics. |
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Low Temp. Phys. 32, 424 (2006); http://dx.doi.org/10.1063/1.2199446 (28 pages) | Cited 42 times
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This is a short review of the theoretical work on the two-dimensional Hubbard model performed in Sherbrooke in the last few years. It is written on the occasion of the twentieth anniversary of the discovery of high-temperature superconductivity. We discuss several approaches, how they were benchmarked and how they agree sufficiently with each other that we can trust that the results are accurate solutions of the Hubbard model. Then comparisons are made with experiment. We show that the Hubbard model does exhibit d-wave superconductivity and antiferromagnetism essentially where they are observed for both hole- and electron-doped cuprates. We also show that the pseudogap phenomenon comes out of these calculations. In the case of electron-doped high temperature superconductors, comparisons with angle-resolved photoemission experiments are nearly quantitative. The value of the pseudogap temperature observed for these compounds in recent photoemission experiments had been predicted by theory before it was observed experimentally. Additional experimental confirmation would be useful. The theoretical methods that are surveyed include mostly the two-particle self-consistent approach, variational cluster perturbation theory (or variational cluster approximation), and cellular dynamical mean-field theory.
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Quantum bits with Josephson junctions (Review Article) Low Temp. Phys. 33, 724 (2007); http://dx.doi.org/10.1063/1.2780165 (21 pages) | Cited 41 times
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Recent demonstrations of macroscopic quantum coherence in Josephson junction based electronic circuits have opened an entirely new dimension for research and applications in the established field of Josephson electronics. In this article we discuss basic Josephson circuits for qubit applications, methods of quantum description of these circuits, and circuit solutions for qubit couplings. Principles of manipulation and readout of superconducting qubits are reviewed and illustrated with recent experiments using various qubit types.
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Features of the magnetoelectric properties of BiFeO3 in high magnetic fields Low Temp. Phys. 27, 478 (2001); http://dx.doi.org/10.1063/1.1382990 (2 pages) | Cited 31 times
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It is shown that the destruction of the cycloidal structure of the magnetic ferroelectric BiFeO3 by a high magnetic field (Hn ≈ 200 kOe) leads to the onset of a linear magnetoelectric effect and the appearance of a toroidal moment. The proof of the existence of a toroidal moment T in a high magnetic field (H>Hn) is based on the experimental observation that the off-diagonal components of the linear ME effect tensor are asymmetric (α12 = −α21 for L‖c, where L is the antiferromagnetic vector), inasmuch as Tz ∼ α12−α21. © 2001 American Institute of Physics. |
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High‐Tc superconductivity mechanisms in copper oxides (A Review) Low Temp. Phys. 22, 1 (1996); http://dx.doi.org/10.1063/1.593085 (32 pages) | Cited 30 times
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An attempt is made to carry out a comparative analysis and to consider the models of pairing mechanisms proposed for describing high‐Tc superconductivity in copper oxides. The main attention is paid to specific features of these compounds reflected in their crystal, electron, and magnetic structure and determining possible mechanisms of pairing which ultimately ensure the formation of a superconducting condensate at a high critical temperature. One of the main aims of the review is a discussion of the unsolved problems in the theory of high‐temperature superconductivity in layered copper oxides. © 1996 American Institute of Physics. |
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Negative thermal expansion of fullerite C60 at liquid helium temperatures Low Temp. Phys. 23, 943 (1997); http://dx.doi.org/10.1063/1.593498 (4 pages) | Cited 30 times
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The thermal expansion of fullerite C60 has been measured in the temperature range 2–9 K. A compacted fullerite sample with a diameter of about 6 mm and height of 2.4 mm was used. It was found that at temperatures below ∼ 3.4 K the linear thermal expansion coefficient becomes negative. At temperatures above 5 K our results are in good agreement with the available literature data. A qualitative explanation of the results is proposed. © 1997 American Institute of Physics. |
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Low Temp. Phys. 29, 228 (2003); http://dx.doi.org/10.1063/1.1542444 (15 pages) | Cited 28 times Online Publication Date: 24 March 2003
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This article reviews our recent work on the ion desorption from adsorbed and condensed molecules at low temperature following the core-level photoexcitations using synchrotron soft x-rays. The systems investigated here are adsorbed molecules with relatively heavy molecular weight, containing third-row elements such as Si, P, S, and Cl. Compared with molecules composed of second-row elements, the highly element-specific and site-specific fragment-ion desorptions are observed when we tune the photon energy at the dipole-allowed 1s→σ∗(3p∗) resonance. On the basis of the resonance Auger decay spectra around the 1s ionization thresholds, the observed highly specific ion desorption is interpreted in terms of the localization of the excited electrons (here called “spectator electrons”) in the antibonding σ∗ orbital. In order to separate the direct photo-induced process from the indirect processes triggered by the secondary electrons, the photon-stimulated ion desorption was also investigated in well-controlled mono- and multilayer molecules. The results confirmed that the resonant photoexcitation not in the substrate but in the thin films of adsorbates plays a significant role in the realization of the highly specific ion desorption. © 2003 American Institute of Physics. |
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Peculiarities of the statics and dynamics of magnetic insulators with single‐ion anisotropy Low Temp. Phys. 20, 775 (1994); http://dx.doi.org/10.1063/1.592878 (26 pages) | Cited 28 times
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We generalize results of the static and dynamic investigations on ferro‐ and antiferro‐ordered magnetic insulators whose anisotropy is brought about by a strong spin‐orbit coupling contribution. An attempt is made to substitute the following assertion: magnetic materials of the above type constitutes a special class, for which the basic restriction of the quasielastics, viz., the conservation of the spin modulus, experiences a substantial violation. We consider qualitatively different cases of strong and weak single‐ion anisotropy for different magnetic symmetry types, zero and finite temperatures, longitudinal and transverse magnetic fields. Questions of the nonlinear dynamics of such magnetic materials and some peculiarities of their optical properties are touched upon. © 1994 American Institue of Physics. |
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On the polyamorphism of fullerite-based orientational glasses Low Temp. Phys. 31, 429 (2005); http://dx.doi.org/10.1063/1.1925371 (16 pages) | Cited 25 times Online Publication Date: 31 May 2005
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A dilatometric investigation in the temperature range 2–28 K shows that a first-order polyamorphous transition occurs in the orientational glasses based on C60 doped with H2, D2 and Xe. A polyamorphous transition is also detected in C60 doped with Kr and He. It is observed that the hysteresis of thermal expansion caused by the polyamorphous transition (and, hence, the transition temperature) is essentially dependent on the type of doping gas. Both positive and negative contributions to the thermal expansion are observed in the low-temperature phase of the glasses. The relaxation time of the negative contribution turns out to be much longer than that of the positive contribution. The positive contribution is found to be due to phonon and libron modes, while the negative contribution is attributed to tunneling states of the C60 molecules. The characteristic time of the phase transformation from the low-T phase to the high-T phase is found for the C60–H2 system at 12 K. A theoretical model is proposed to interpret these observed phenomena. The theoretical model proposed includes a consideration of the nature of polyamorphism in glasses, as well as the thermodynamics and kinetics of the transition. A model of noninteracting tunneling states is used to explain the negative contribution to the thermal expansion. The experimental data obtained are considered within the framework of the theoretical model. From the theoretical model the order of magnitude of the polyamorphous transition temperature is estimated. It is found that the late stage of the polyamorphous transformation is described well by the Kolmogorov law with an exponent of n=1. At this stage of the transformation, the two-dimensional phase boundary moves along the normal, and the nucleation is not important. © 2005 American Institute of Physics. |
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Low-temperature thermal expansion of pure and inert-gas-doped fullerite C60 Low Temp. Phys. 29, 324 (2003); http://dx.doi.org/10.1063/1.1542477 (9 pages) | Cited 25 times Online Publication Date: 23 April 2003
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The low-temperature (2–24 K) thermal expansion of pure (single-crystal and polycrystalline) C60 and polycrystalline C60 intercalated with He, Ne, Ar, and Kr is investigated using a high-resolution capacitance dilatometer. The investigation of the time dependence of the sample length variations ΔL(t) on heating by ΔT shows that the thermal expansion is determined by the sum of positive and negative contributions, which have different relaxation times. The negative thermal expansion usually prevails at helium temperatures. The positive expansion is connected with the phonon thermalization of the system. The negative expansion is caused by reorientation of the C60 molecules. It is assumed that the reorientation is of a quantum character. The inert gas impurities affect the reorientation of the C60 molecules very strongly, especially at liquid-helium temperatures. A temperature hysteresis of the thermal expansion coefficient of Kr– and He–C60 solutions is revealed. The hysteresis is attributed to orientational polymorphous transformation in these systems. © 2003 American Institute of Physics. |
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Observation of the electric induction due to a second-sound wave in He II Low Temp. Phys. 30, 994 (2004); http://dx.doi.org/10.1063/1.1820042 (4 pages) | Cited 23 times Online Publication Date: 14 December 2004
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It is shown experimentally that the relative motion of the superfluid and normal components of He II in a second-sound wave is accompanied by the appearance of electric induction. The process is reversible. It is shown that the amplitude ratio of the temperature and induction potential oscillations is a temperature-independent constant equal to 2.3×104 K/V. © 2004 American Institute of Physics. |
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Scattering theory of superconductive tunneling in quantum junctions Low Temp. Phys. 23, 181 (1997); http://dx.doi.org/10.1063/1.593475 (18 pages) | Cited 23 times
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A consistent theory of superconductive tunneling in single-mode junctions within a scattering formulation of Bogolyubov-de Gennes quantum mechanics is presented. The dc Josephson effect and the dc quasiparticle transport in the voltage-biased junctions are considered. Elastic quasiparticle scattering by the junction determines the equilibrium Josephson current. The origin of Andreev bound states in tunnel junctions and their role in equilibrium Josephson transport are discussed. In contrast, quasiparticle tunneling in voltage-biased junctions is determined by inelastic scattering. A general expression for inelastic scattering amplitudes is derived and the quasiparticle current is calculated at all voltages with emphasis on a discussion of the properties of subgap tunnel current and the nature of subharmonic gap structure. © 1997 American Institute of Physics. |
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Calculated optical properties of heavy metals. I. Relativistic formalism and cubic 5d metals Low Temp. Phys. 19, 494 (1993); http://dx.doi.org/10.1063/1.592553 (12 pages) | Cited 22 times
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The formalism for calculation of the optical properties of solids within the random phase approximation and the relativistic linear muffin‐tin‐orbital method is presented. The method is applied to the cubic 5d metals Ta, W, Ir, Pt, and Au using the local density approximation. The band structures, the lj projected densities of states, the complex dielectric functions, the optical conductivities, and the electron energy‐loss spectra are evaluated in the energy range from 0 to 30 eV. Good agreement with the experimental data is found. |
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Composite magnetostrictive materials for advanced automotive magnetomechanical sensors Low Temp. Phys. 27, 266 (2001); http://dx.doi.org/10.1063/1.1365598 (9 pages) | Cited 22 times
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In this paper we present the development of a composite magnetostrictive material for automotive applications. The material is based on cobalt ferrite, CoO⋅Fe2O3, and contains a small fraction of metallic matrix phase that serves both as a liquid-phase sintering aid during processing and enhances the mechanical properties over those of a simple sintered ferrite ceramic. In addition the metal matrix makes it possible to braze the material, making the assembly of a sensor relatively simple. The material exhibits good sensitivity and should have high corrosion resistance, while at the same time it is low in cost. © 2001 American Institute of Physics. |
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Three-phonon interactions and initial stage of phonon pulse evolution in He II Low Temp. Phys. 25, 488 (1999); http://dx.doi.org/10.1063/1.593772 (5 pages) | Cited 22 times
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An expression for the characteristic rate of three-phonon processes in superfluid 4He, which is valid in the entire range of phonon energies where three-phonon processes are allowed is derived proceeding from the hydrodynamic Landau Hamiltonian. Possible limiting cases are analyzed and compared with the results of previous investigations. It is found that three-phonon processes completely govern the initial relaxation of a phonon pulse injected into He II by a heated solid. As a result, the equilibrium form of phonon distribution is established in the anomalous region of phonon dispersion over a time interval of the order of 10−10 s. © 1999 American Institute of Physics. |
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Superconductors with charge- and spin-density waves: theory and experiment (Review) Low Temp. Phys. 26, 305 (2000); http://dx.doi.org/10.1063/1.593902 (26 pages) | Cited 20 times
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The properties of existing superconductors with ejectron spectrum instabilities, namely charge-density waves (CDWs) and spin-density waves (SDWs), are reviewed. In such substances the superconducting gap exists over the whole Fermi surface, whereas the dielectric gap emerges only on its nested sections. In particular, CDW superconductors include layered dichalcogenides, NbSe3, compounds with the A15 and C15 structures, etc. There is a lot of evidence that high-Tc oxides also belong to this group of materials. SDW superconductors include, e.g., URu2Si2 and related heavy-fermion compounds, Cr–Re alloys and organic superconductors. The theoretical description given in this review is based mostly on the Bilbro-McMillan model of the partially dielectrized metal. Various thermodynamic and electrodynamic properties are calculated in the framework of this model. The main subject of the review is the nonstationary Josephson effect in tunnel junctions involving CDW or SDW superconductors. A new effect of symmetry breaking in symmetrical tunnel junctions is predicted by the authors. A comparison with experiment is given. © 2000 American Institute of Physics. |
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Low Temp. Phys. 32, 406 (2006); http://dx.doi.org/10.1063/1.2199443 (18 pages) | Cited 20 times
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This review is written at the time of the twentieth anniversary of the discovery of high-temperature superconductors, which nearly coincides with the important discovery of the superfluid phases of ultracold trapped fermionic atoms. We show how these two subjects have much in common. Both have been addressed from the perspective of the BCS—Bose–Einstein condensation (BEC) crossover scenario, which is designed to treat short coherence length superfluids with transition temperatures which are “high” with respect to the Fermi energy. A generalized mean field treatment of BCS–BEC crossover at general temperatures T, based on the BCS–Leggett ground state, has met with remarkable success in the fermionic atomic systems. Here we summarize this success in the context of four different cold atom experiments, all of which provide indications, direct or indirect, for the existence of a pseudogap. This scenario also provides a physical picture of the pseudogap phase in the underdoped cuprates which is a central focus of high Tc research. We summarize successful applications of BCS–BEC crossover to key experiments in high Tc systems, including the phase diagram, specific heat, and vortex core STM data, along with the Nernst effect, and exciting recent data on the superfluid density in very underdoped samples.
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Vortex matter in superconductors Low Temp. Phys. 27, 732 (2001); http://dx.doi.org/10.1063/1.1401182 (15 pages) | Cited 19 times
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The behavior of the ensemble of vortices in the Shubnikov phase in biaxially oriented films of the high-temperature superconductor YBa2Cu3O7−δ (YBCO) in an applied magnetic field is investigated for different orientations of the field. The techniques used are the recording of the current–voltage characteristics in the transport current and of resonance curves and damping of a mechanical oscillator during the passage of a transport current. It is shown that the behavior of the vortex ensemble in YBCO films, unlike the case of single crystals, is determined by the interaction of the vortices with linear defects—edge dislocations, which are formed during the pseudomorphic epitaxial growth and are the dominant type of defect of the crystal lattice, with a density reaching 1015 lines/m2. The effective pinning of the vortices and the high critical current density (Jc ≥ 3×1010 A/m2 at 77 K) in YBCO films are due precisely to the high density of linear defects. New phase states of the vortex matter in YBCO films are found and are investigated in quasistatics and dynamics; they are due to the interaction of the vortices with crystal defects, to the onset of various types of disordering of the vortex lattice, and to the complex depinning process. A proposed H–T phase diagram of the vortex matter for YBCO films is proposed.© 2001 American Institute of Physics. |
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Low Temp. Phys. 21, 364 (1995); http://dx.doi.org/10.1063/1.592951 (3 pages) | Cited 19 times
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Structure, microhardness and slip systems were studied in C60 crystals of high purity in the temperature range 30–290 K, which includes the fcc→sc phase transition at Tc=260 K and the orientational glass region T<100 K. A step‐like change of both the lattice parameter and the microhardness when passing through Tc have been recorded, as well as the formation of slip tracks near the indentations in both phases. The slip system 〈110〉{111}, operative at room temperature in the fcc phase, is shown to retain its activity below Tc, in the sc phase. In the region where the orientational glass is formed, we have found a kink‐like anomaly on the microhardness vs temperature curve; this anomaly correlates with a weak anomaly in the temperature dependence of the lattice parameter. Assumptions are formulated concerning the character of the dislocation motion in C60 crystals, which make it possible to explain the microplasticity anomalies observed. © 1995 American Institute of Physics. |
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