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1.


    GEKHT, R. S.
    MAGNETIC-STRUCTURES AND PROPERTIES OF STATES IN STRONGLY FRUSTRATED HEISENBERG ANTIFERROMAGNETS / R. S. GEKHT // Zhurnal Eksperimentalnoi Teor. Fiz. - 1992. - Vol. 102, Is. 6. - P. 1968-1982. - Cited References: 23 . - ISSN 0044-4510
РУБ Physics, Multidisciplinary
Рубрики:
PHASE-TRANSITIONS
   SPIN

   LATTICE

   MODELS

   LONG

Аннотация: The magnetic structures and properties of states in frustrated Heisenberg antiferromagnets are analyzed. It is shown that frustrations induced due to additional spins in the system lead to a large variety of phase with the commensurable and uncommensurable periods and also to arising nonperiodical phases. The energy spectrum of states is studied. It is found that in the large region of the frustration parameter variation the modulated phase (0, Q) is unstable. The phase diagram of states is found and the region of local degeneration for some structures is indicated.

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2.


    GEKHT, R. S.
    ON MAGNETIC STATES IN STRONGLY FRUSTRATED 2-DIMENSIONAL ANTIFERROMAGNETICS / R. S. GEKHT, V. V. GRISHIN // Fiz. Tverd. Tela. - 1992. - Vol. 34, Is. 11. - P. 3557-3559. - Cited References: 5 . - ISSN 0367-3294
РУБ Physics, Condensed Matter
Рубрики:
PHASE-TRANSITIONS
   LATTICE


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Держатели документа:
LV KIRENSKII INST PHYS,KRASNOYARSK,RUSSIA
ИФ СО РАН

Доп.точки доступа:
GRISHIN, V. V.
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3.


    Aplesnin, S. S.
    Influence of quantum fluctuations on the Neel temperature of a dilute two-dimensional anisotropic antiferromagnet / S. S. Aplesnin // Phys. Solid State. - 1997. - Vol. 39, Is. 5. - P. 800-802, DOI 10.1134/1.1130121. - Cited References: 15 . - ISSN 1063-7834
РУБ Physics, Condensed Matter
Рубрики:
LATTICE
Аннотация: A quantum Monte Carlo procedure is used to calculate the energy, sublattice magnetization, Neel temperature, and the slopes of the S=[l/T-N(x=0)]dT(N)(x)/dx curves as functions of the hole concentration and the exchange anisotropy Delta=1-J(x,y)/J(z) in the Heisenberg model with anisotropic negative interactions between nearest neighbors in a square lattice with dilution among the lattice sites. The slope diverges in the limit Delta--0:S similar to ln(6.5/Delta). (C) 1997 American Institute of Physics.

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Держатели документа:
L. V. Kirenskii Inst. of Phys., Siberian Branch, Russian Academy of Sciences, 660036 Krasnoyarsk, Russian Federation
ИФ СО РАН

Доп.точки доступа:
Аплеснин, Сергей Степанович
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4.


    Kuz'min, E. V.
    Effect of frustrations on magnetism in the Ru double perovskite Sr2YRuO6 / E. V. Kuz'min, S. G. Ovchinnikov, D. J. Singh // Phys. Rev. B. - 2003. - Vol. 68, Is. 2. - Ст. 24409, DOI 10.1103/PhysRevB.68.024409. - Cited References: 24 . - ISSN 1098-0121
РУБ Physics, Condensed Matter
Рубрики:
MOTT TRANSITION
   LATTICE

   SPIN

   ANTIFERROMAGNETISM

   SUPERCONDUCTIVITY

   FERROMAGNETISM

Аннотация: Localized Ru5+ spins in Sr2YRuO6 form a fcc lattice with an antiferromagnetic (AFM) nearest-neighbor (NN) coupling J approximate to 25 meV and rather low Neel temperature T-N= 26 K. Analysis of the electronic structure of Sr2RuO4 results in the effective Heisenberg model. We have studied the effect of frustrations on the AFM type-I structure of Sr2YRuO6 in the spin-wave approximation. In the model with only NN coupling the AFM state is unstable due to frustrations, and T-N = 0. Stabilization of the AFM state occurs due to the next-nearest-neighbor coupling I or due to the magnetic anisotropy D. Very small values D/J similar to I/J less than or equal to 10(-3) are enough to obtain the experimental values of T-N and sublattice magnetization m = 1.85 mu(B) /Ru (62% from the nominal S = 3/2 value).

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Держатели документа:
Krasnoyarsk State Univ, Krasnoyarsk 660074, Russia
Russian Acad Sci, Siberian Branch, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
USN, Res Lab, Ctr Computat Mat Sci, Washington, DC 20375 USA
ИФ СО РАН

Доп.точки доступа:
Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Singh, D. J.
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5.


    Korshunov, M. M.
    Generalization of Luttinger's theorem for strongly correlated electron systems / M. M. Korshunov, S. G. Ovchinnikov // Phys. Solid State. - 2003. - Vol. 45, Is. 8. - P. 1415-1422, DOI 10.1134/1.1602872. - Cited References: 19. - The authors are grateful to V.V. Val’kov for helpful remarks. This work was supported by the INTAS (grant no. INTAS-01-0654), the Russian Foundation for Basic Research and the Krasnoyarsk KraÏ Science Foundation (program “EniseÏ,” project no. 02-02-97705), the program of the Russian Academy of Sciences “Quantum Macrophysics,” and the Russian Academy of Sciences, Siberian Division (Lavrent’yev Contest for Youth Projects) . - ISSN 1063-7834
РУБ Physics, Condensed Matter
Рубрики:
NARROW ENERGY BANDS
   HUBBARD-MODEL

   FERMI-SURFACE

   LATTICE

Аннотация: By on the analyzing the general structure of the Green function of a strongly correlated electron system, it is shown that, for the regime of strong correlations, Luttinger's theorem should be generalized in the following way: the volume of the Fermi surface of the system of noninteracting particles is equal to that of the quasiparticles in the strongly correlated system with due regard for the spectral weight of the quasiparticles. An investigation of the t-J model and of the Hubbard model, as applied to the paramagnetic nonsuperconducting phase, shows that the generalized Luttinger theorem is valid for these models. (C) 2003 MAIK "Nauka/Interperiodica".

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Публикация на русском языке Коршунов, Максим Михайлович. Обобщение теоремы Латтинжера для систем с сильными электронными корреляциями [Текст] / М. М. Коршунов, С. Г. Овчинников // Физ. тверд. тела. - 2003. - Т. 45 Вып. 8. - С. 1351-1357

Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk 660036, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk 660036, Russian Federation

Доп.точки доступа:
Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Коршунов, Максим Михайлович
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6.


    Gekht, R. S.
    A quantum spin liquid in a two-layer triangular antiferromagnet / R. S. Gekht, I. N. Bondarenko // J. Exp. Theor. Phys. - 2005. - Vol. 101, Is. 5. - P. 868-880, DOI 10.1134/1.2149066. - Cited References: 43 . - ISSN 1063-7761
РУБ Physics, Multidisciplinary
Рубрики:
ONE-DIMENSIONAL ANTIFERROMAGNETS
   DIMER GROUND-STATE

   MEAN-FIELD THEORY

   HEISENBERG-ANTIFERROMAGNET

   SYSTEM SRCU2(BO3)(2)

   PHASE-TRANSITION

   GAP

   FLUCTUATIONS

   EXCITATIONS

   LATTICE

Кл.слова (ненормированные):
Antiferromagnetic materials -- Magnetic fields -- Magnetization -- Phase diagrams -- Spectrum analysis -- Thermodynamics -- Analogous systems -- Square lattices -- Thermodynamic quantities -- Two-layer triangular antiferromagnets -- Quantum theory
Аннотация: The possibility of implementing a quantum-spin-liquid-type state in a two-layer triangular spin-1/2 antiferromagnet at T = 0 is investigated. The ratio of intra- to interlayer exchange constants (j) is found under which a transition from the classical state with 120 degrees triangular order to a quantum state with zero magnetization per site occurs; in this case, the spins of adjacent layers form singlets that are separated from triplet excitations by an energy gap. Compared with an analogous system with the square lattice, the range of j in which the classical ordered state is realized turns out to be an order of magnitude smaller due to the effects of frustration; in this case, the behavior of thermodynamic quantities is analogous, on the whole, to that in two-layer square lattices; a difference manifests itself in the behavior of the gap in the spectrum of quasiparticles in an external magnetic field h. For small fields h, a j-h phase diagram is constructed that determines the domains in which the 120 degrees and the singlet phases exist. It is established that, in the neighborhood of the second-order phase transition, the contribution, to the thermodynamic quantities, of longitudinal spin fluctuations, which are disregarded in the spin-wave description, is comparable to the contribution of transverse fluctuations. (c) 2005 Pleiades Publishing, Inc.

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Держатели документа:
Russian Acad Sci, Kirenskii Inst Phys, Siberian Div, Krasnoyarsk 660036, Russia
ИФ СО РАН
Kirenskii Institute of Physics, Siberian Division, Russian Academy of Sciences, Krasnoyarsk, Akademgorodok, 660036, Russian Federation

Доп.точки доступа:
Bondarenko, I. N.
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7.


    Martynov, S. N.
    Frustration mechanism of formation of a helical magnetic structure in the CuB2O4 two-subsystem antiferromagnet / S. N. Martynov, A. D. Balaev // JETP Letters. - 2007. - Vol. 85, Is. 12. - P. 649-654, DOI 10.1134/S0021364007120132. - Cited References: 21 . - ISSN 0021-3640
РУБ Physics, Multidisciplinary
Рубрики:
PHASE 10 K
   COPPER METABORATE

   LATTICE

Аннотация: A new mechanism is proposed for forming an incommensurate magnetic structure of the transverse helix type owing to the removal of frustration through intersubsystem exchange in a two-subsystem antiferromagnet. The symmetry analysis of the distribution of the Dzyaloshinskii-Moriya interaction and comparison with the experimental data on the field dependence of magnetization indicate that antisymmetric exchange and competition between symmetric exchanges cannot be responsible for forming a helical magnetic structure in CuB2O4.

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Держатели документа:
Siberian Fed Univ, Krasnoyarsk 660041, Russia
Russian Acad Sci, Siberian Div, Kirensky Inst Phys, Krasnoyarsk 660036, Russia
ИФ СО РАН
Siberian Federal University, Krasnoyarsk 660041, Russian Federation
Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk 660036, Russian Federation

Доп.точки доступа:
Balaev, A. D.; Балаев, Александр Дмитриевич; Мартынов, Сергей Николаевич
}
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8.


    Val'kov, V. V.
    EFFECTIVE INTERACTIONS IN THE PERIODIC ANDERSON MODEL IN THE REGIME OF MIXED VALENCY WITH STRONG CORRELATIONS / V. V. Val'kov, D. M. Dzebisashvili // Theor. Math. Phys. - 2008. - Vol. 157, Is. 2. - P. 1565-1576, DOI 10.1007/s11232-008-0130-8. - Cited References: 19. - This work was supported in part by the Russian Foundation for Basic Research (Grant No. 07-02-00226), a program of the Branch of Physical Sciences, Russian Academy of Sciences, and the "Integration Project" of the Siberian Branch, Russian Academy of Sciences. . - ISSN 0040-5779
РУБ Physics, Multidisciplinary + Physics, Mathematical
Рубрики:
LATTICE
Кл.слова (ненормированные):
periodic Anderson model -- mixed valency -- heavy fermion -- effective Hamiltonian -- superconductivity -- Effective Hamiltonian -- Heavy fermion -- Mixed valency -- Periodic Anderson model -- Superconductivity
Аннотация: For the periodic Anderson model in the strong correlation regime, we construct the effective Hamiltonian H(eff) up to terms of the fourth order in the parameter V/U, where V is the hybridization interaction intensity and U is the intra-atom Coulomb repulsion strength. This Hamiltonian contains interactions inducing both magnetic ordering and Cooper instability under conditions of a mixed valency of rare-earth ions. Based on numerical calculations, we obtain information about the dependences of the effective interaction parameters on the distance between crystal lattice sites. We demonstrate that realizing exchange interactions corresponds to a strongly frustrated system of localized spin moments and facilitates the suppression of the antiferromagnetic order parameter with a possible transition to the state of a quantum spin liquid. It is essential that among the terms in H(eff) inducing the transition to the superconductivity phase, there are terms resulting in the d-type symmetry of the superconductivity order parameter; such a symmetry is realized in many heavy-fermion compounds.

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Держатели документа:
[Val'kov, V. V.
Dzebisashvili, D. M.] RAS, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Branch, RAS, Krasnoyarsk, Russian Federation
Siberian Federal University, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Dzebisashvili, D. M.; Дзебисашвили, Дмитрий Михайлович; Вальков, Валерий Владимирович
}
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9.


    Val'kov, V. V.
    Spin-Fluctuation Renormalization of the Temperature of a Superconducting s-Phase in Rare-Earth Intermetallides / V. V. Val'kov, D. M. Dzebisashvili // J. Exp. Theor. Phys. - 2008. - Vol. 107, Is. 4. - P. 679-691, DOI 10.1134/S1063776108100166. - Cited References: 34. - This study was supported in part by the Russian Foundation for Basic Research ( project no. 07-02-00226), the Department of Physic of the Russian Academy of Sciences ( within the program "Strongly Correlated Electrons in Semiconductors, Superconductors, and Magnetic Materials"), and the Siberian Branch of the Russian Academy of Sciences ( integration project no. 3.4). . - ISSN 1063-7761
РУБ Physics, Multidisciplinary
Рубрики:
HEAVY-FERMION SUPERCONDUCTORS
   PERIODIC ANDERSON MODEL

   WAVE SUPERCONDUCTIVITY

   PERTURBATION-THEORY

   MECHANISM

   VALENCE

   SYSTEMS

   LATTICE

   STATE

Кл.слова (ненормированные):
Differential equations -- Electric conductivity -- Green's function -- Numerical analysis -- Rare earth elements -- Spin dynamics -- Spin fluctuations -- Anomalous components -- Critical temperatures -- Experimental datums -- Infinite systems -- Numerical calculations -- Order parameters -- Periodic Anderson models -- Renormalization -- S-phase -- Skutterudite -- Strong electron correlations -- Sub systems -- Superconducting states -- Superconductivity
Аннотация: A theory of the superconducting state with s-type symmetry of the order parameter ( the transition to this state was observed in recently discovered heavy-fermion skutterudite LaFe(4)P(12)) is developed using the periodic Anderson model in the limit of strong electron correlations. Exact representations of Green's functions of the superconducting phase via the normal and anomalous components of the mass and strength operators are obtained. It is shown that an important role in the description of this superconducting phase is played by the anomalous components of the strength operator, which reflect spin-fluctuation processes in the localized subsystem. These components are calculated in the one-loop approximation using the solution of an infinite system of integral equations of self-consistency for the superconducting phase. Numerical calculations show that allowance for the process of scattering on spin fluctuations leads to renormalization of the critical temperature and provides agreement with the experimental data.

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Держатели документа:
[Val'kov, V. V.
Dzebisashvili, D. M.] Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
[Val'kov, V. V.
Dzebisashvili, D. M.] Siberian Fed Univ, Krasnoyarsk 660041, Russia
[Val'kov, V. V.] Siberian State Aerosp Univ, Krasnoyarsk 660014, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russian Federation
Siberian Federal University, Krasnoyarsk 660041, Russian Federation
Siberian State Aerospace University, Krasnoyarsk 660014, Russian Federation

Доп.точки доступа:
Dzebisashvili, D. M.; Дзебисашвили, Дмитрий Михайлович; Вальков, Валерий Владимирович
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10.


    Kolovsky, A. R.
    Energetically constrained co-tunneling of cold atoms / A. R. Kolovsky, J. Link, S. Wimberger // New J. Phys. - 2012. - Vol. 14. - Ст. 75002, DOI 10.1088/1367-2630/14/7/075002. - Cited References: 18. - The present project was supported by the Excellence Initiative (Enable Fund of the Faculty of Physics and Astronomy, Heidelberg University). Moreover, SW acknowledges financial support from the DFG through FOR760, the Helmholtz Alliance Program of the Helmholtz Association (contract number HA-216: Extremes of density and temperature: cosmic matter in the laboratory), and by the Heidelberg Graduate School of Fundamental Physics (grant number GSC 129/1) and AK acknowledges support from the Russian Foundation for Basic Research (project number 12-02-000094-a: Tunneling of the macroscopic quantum states) and by the Siberian Branch of RAS (project no. 29: Dynamics of atomic Bose-Einstein condensates in optical lattices). AK is very grateful for the hospitality of the Institute of Theoretical Physics of Heidelberg University. . - ISSN 1367-2630
РУБ Physics, Multidisciplinary
Рубрики:
LATTICE
Аннотация: We study under-barrier tunneling for a pair of energetically bound bosonic atoms in an optical lattice with a barrier. We identify the conditions under which this exotic molecule tunnels as a point particle with the coordinate given by the bound pair center of mass and discuss the atomic co-tunneling beyond this regime. In particular, we quantitatively analyze resonantly enhanced co-tunneling, where two interacting atoms penetrate the barrier with higher probability than a single atom.

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Держатели документа:
[Kolovsky, Andrey R.] LV Kirenskii Inst Phys, Krasnoyarsk 660036, Russia
[Kolovsky, Andrey R.] Siberian Fed Univ, Krasnoyarsk 660041, Russia
[Link, Julia
Wimberger, Sandro] Univ Heidelberg, Inst Theoret Phys, D-69120 Heidelberg, Germany

Доп.точки доступа:
Link, J.; Wimberger, S.; Коловский, Андрей Радиевич
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