Publications (78)105.95 Total impact

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ABSTRACT: In threedimensional electron systems with a high electron density it is not possible to reach the Anderson transition neither by increasing disorder nor by a combination of static disorder with a dynamic one (by high temperature), or by selecting a material with a large deformation potential and a large constant of electronphonon interaction. 
Article: Mooij Rule and Weak Localization
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ABSTRACT: It has been shown that the observed correlation between the resistivity $\rho$ of highresistive metallic alloys and the sign of the temperature derivative $d\rho/dT$ can be explained by taking into account the weak localization. This correlation is known as Mooij rule: the derivative $d\rho/dT$ is negative for alloys with resistivity in the range of $300\div150\,\mu\Omega\cdot$cm, which corresponds to the electron mean free path about the interatomic distance; however, this derivative is positive for alloys with lower resistivity. 
Article: Localized superconducting pairs
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ABSTRACT: Different physical phenomena are discussed which should help to comprehend and interpret the concept of localized superconductive pairs; these include behavior of highly resistive granular materials with superconducting grains, parity effect and the BerezinskiiKosterlitzThouless transition. Experimental arguments in support of localized pairs existence are presented and conditions which promote their appearance are analyzed.  [Show abstract] [Hide abstract]
ABSTRACT: The current understanding of the superconductorinsulator transition is discussed level by level in a cyclic spirallike manner. At the first level, physical phenomena and processes are discussed which, while of no formal relevance to the topic of transitions, are important for their implementation and observation; these include superconductivity in low electron density materials, transport and magnetoresistance in superconducting island films and in highly resistive granular materials with superconducting grains, and the BerezinskiiKosterlitzThouless transition. The second level discusses and summarizes results from various microscopic approaches to the problem, whether based on the BardeenCooperSchrieffer theory (the disorderinduced reduction in the superconducting transition temperature; the key role of Coulomb blockade in highresistance granular superconductors; superconducting fluctuations in a strong magnetic field) or on the theory of the BoseEinstein condensation. A special discussion is given to phenomenological scaling theories. Experimental investigations, primarily transport measurements, make the contents of the third level and are for convenience classified by the type of material used (ultrathin films, variable composition materials, hightemperature superconductors, superconductorpoor metal transitions). As a separate topic, data on nonlinear phenomena near the superconductorinsulator transition are presented. At the final, summarizing, level the basic aspects of the problem are enumerated again to identify where further research is needed and how this research can be carried out. Some relatively new results, potentially of key importance in resolving the remaining problems, are also discussed.  [Show abstract] [Hide abstract]
ABSTRACT: The current understanding of the superconductorinsulator transition is discussed level by level in a cyclic spirallike manner. At the first level, physical phenomena and processes are discussed which, while of no formal relevance to the topic of transitions, are important for their implementation and observation; these include superconductivity in low electron density materials, transport and magnetoresistance in superconducting island films and in highly resistive granular materials with superconducting grains, and the BerezinskiiKosterlitzThouless transition. The second level discusses and summarizes results from various microscopic approaches to the problem, whether based on the BardeenCooperSchrieffer theory (the disorderinduced reduction in the superconducting transition temperature; the key role of Coulomb blockade in highresistance granular superconductors; superconducting fluctuations in a strong magnetic field) or on the theory of the BoseEinstein condensation. A special discussion is given to phenomenological scaling theories. Experimental investigations, primarily transport measurements, make the contents of the third level and are for convenience classified by the type of material used (ultrathin films, variable composition materials, hightemperature superconductors, superconductorpoor metal transitions). As a separate topic, data on nonlinear phenomena near the superconductorinsulator transition are presented. At the final, summarizing, level the basic aspects of the problem are enumerated again to identify where further research is needed and how this research can be carried out. Some relatively new results, potentially of key importance in resolving the remaining problems, are also discussed. 

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ABSTRACT: Metalinsulator transitions and transitions between different quantum Hall liquids are used to describe the physical ideas forming the basis of quantum phase transitions and the methods of application of theoretical results in processing experimental data. The following two theoretical schemes are discussed and compared: the general theory of quantum phase transitions, which has been developed according to the theory of thermodynamic phase transitions and relies on the concept of a partition function, and a theory which is based on a scaling hypothesis and the renormalizationgroup concept borrowed from quantum electrodynamics, with the results formulated in terms of flow diagrams. Comment: 27 pages, 20 figures 



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ABSTRACT: Various experimental observations of the superconductorinsulator transition are described and compared with two theoretical models: one based on bosonvortex duality and the other where the superconducting fluctuations at low temperatures in the magnetic field are calculated. The latter shows that the superconducting fluctuations in dirty but homogeneous superconductor act as grains in a granular superconductor. When superconductivity is destroyed by changing some of parameters, either intrinsic (carriers density, level of disorder) or extrinsic (magnetic field) ones, the material can turn not only into normal metal but into insulator as well. We’ll discuss here magneticfieldinduced superconductorinsulator transitions (SIT). Magnetic field transfers the superconductor into insulator in the case when the carrier density in the material is low and the level of disorder is high, so that without the superconductivity the material would be in zero field on the insulating side of the metalinsulating transition. The main sign of SIT is the fanlike set of the resistance curves R(T ): they go down with decreasing of the temperature at fields below the critical, BB c. The list of materials which displayed such type of behaviour contains amorphous MoxGe1−x [1] and MoxSi1−x [2] films, amorphous InOx films [3, 4], ultrathin films of Be [5], crystalline films of Nd2−xCexCuO4+y [6, 7]. Two typical examples of such sets of curves relevant to different limits are presented in Figs. 1 and 2. In Nd2−xCexCuO4+y (Fig. 1) the growth of the resistance with decreasing temperature on the nonsuperconducting side of the fieldinduced transition was below ten percent so that it reminded more a metal with quantum corrections to its conductivity than an insulator. In amorphous InOx (Fig. 2), typical for insulator exponential temperature dependence of the resistance resulted in almost tenfold increase of the resistance.  [Show abstract] [Hide abstract]
ABSTRACT: Nonequilibrium electrons are produced by interband monochromatic photoexcitation in the directbandgap semiconductor pInSb at helium temperatures. The study of magnetoimpurity shows that conductivity in crossed electric and quantizing magnetic fields has a negative part, due to the distortion of the photoelectron distribution function. In a quantizing magnetic field, excitons decay at ionized acceptors resonantly with respect to the magnetic field, the decay of probability increases sharply each time he electron occupies a Landau level. It is observed that for all the complexity of the nonequilibrium system, the keypoint of of change at a resonance is an increase in the concentration of nonequilibrium electrons. 

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ABSTRACT: Various experimental observations of the magneticfieldinduced superconductor–insulator transition are described and compared with different theoretical models: one based on boson–vortex duality, next exploring the properties of granular superconductors and the third analyzing effect of the superconducting fluctuations in the magnetic field at low temperature. All the models point to the existence of pairwise electron correlations at the Fermilevel of the insulator. These socalled localized pairs should vanish in high magnetic fields. The localized pairs apparently come from the parity effect in ultrasmall quasigrains––local minima of the random potential which can admit only small limited number of electrons.  [Show abstract] [Hide abstract]
ABSTRACT: Magnetotransport of superconducting Nd2−x CexCuO4+y (NdCeCuO) films is studied in the temperature interval 0.3–30 K. The microscopic theory of the quantum corrections to conductivity, both in the Cooper and in the diffusion channels, qualitatively describes the main features of the experiment, including the negative magnetoresistance in the highfield limit. Comparison with the model of the fieldinduced superconductorinsulator transition is included and a crossover between these two theoretical approaches is discussed. 
Article: Chemical localization
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ABSTRACT: The possibility that, in spite of high valence electron concentrations, metalinsulator transitions can in principle occur in materials composed of atoms of only metallic elements is demonstrated based on the analysis of experimental data. For such a transition to occur, stable atomic configurations forming deep potential wells capable of trapping dozens of valence electrons should appear in the system. This means, in essence, that bulk metallic medium transforms into an assembly of identical quantum dots. Depending on the parameters, such a material either does contain delocalized electrons (metal) or does not contain such electrons (insulator). The degree of disorder is one of these parameters. Two types of substances with such properties are discussed: liquid binary alloys with both components being metallic, and thermodynamically stable quasicrystals.
Publication Stats
620  Citations  
105.95  Total Impact Points  
Top Journals
Institutions

20112013

Moscow Institute of Physics and Technology
Moskva, Moscow, Russia


19962010

Russian Academy of Sciences
 Institute of Solid State Physics
Moskva, Moscow, Russia 
Radboud University Nijmegen
 High Field Magnet Laboratory (HFML)
Nymegen, Gelderland, Netherlands


19942005

Institute of Solid State Physics RAS
Chernogolovka, Moskovskaya, Russia
