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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Makarov I. A., Zotova M. V., Ovchinnikov S. G.
Заглавие : 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
Коллективы : Russian Foundation for Basic Research [16-02-00098]; Basic Research Program of the Presidium of the Russian Academy of Sciences [12]
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 126, Is. 5. - P.683-698. - ISSN 1063-7761, DOI 10.1134/S1063776118050059. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 58. - We are grateful to V.I. Zinenko and V.A. Gavrichkov for useful discussions. This work was financially supported by the Russian Foundation for Basic Research (project no. 16-02-00098) and the Basic Research Program no. 12 of the Presidium of the Russian Academy of Sciences ("Fundamental Problems of High-Temperature Superconductivity").
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
D-WAVE SUPERCONDUCTIVITY
LATTICE
Аннотация: 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.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Komarov K. K., Dzebisashvili D. M.
Заглавие : Effective indirect multi-site spin-spin interactions in the s-d(f) model
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН , Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund [16-42-240435, 16-42-243057]; Russian Federation [MK-1398.2017.2]
Место публикации : J. Magn. Magn. Mater.: Elsevier Science, 2017. - Vol. 440: EURO-Asian Symposium on Trends in Magnetism (EASTMAG) (AUG 15-19, 2016, Siberian Fed Univ, Krasnoyarsk, RUSSIA). - P.57-59. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2016.12.075. - ISSN 1873-4766(eISSN)
Примечания : Cited References:21. - The work was supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research (project nos. 16-42-240435, and 16-42-243057). The work of K.K. Komarov was supported by the grant of the President of the Russian Federation (Project MK-1398.2017.2).
Предметные рубрики: BIQUADRATIC EXCHANGE
LATTICE
Ключевые слова (''Своб.индексиров.''): s-d(f) exchange model--mult i-site spin-spin interactions
Аннотация: Using the diagram technique for Matsubara Green's functions it is shown that the dynamics of the localized spin subsystem in the s-d(f) model can be described in terms of an effective spin model with multi-site spin-spin interactions. An exact representation of the action for the effective purely spin model is derived as an infinite series in powers of s-d(f) exchange interaction J. The indirect interactions of the 2nd, 3rd and 4th order are discussed.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M.
Заглавие : Dynamicalmagnetic susceptibility in the spin-fermion model for cuprate superconductors
Коллективы : Russian Foundation for Basic Research [16-02-00073]; Krasnoyarsk Kray Foundation for Scientific and Technical Progress [16-42-240435]; Siberian Branch of the Russian Academy of Sciences [II.2P, 0356-2015-0405]; Administration of Krasnoyarsk Kray
Место публикации : Theor. Math. Phys. - 2017. - Vol. 193, Is. 3. - P.1853-1864. - ISSN 0040-5779, DOI 10.1134/S004057791712011X. - ISSN 1573-9333(eISSN)
Примечания : Cited References:35. - This research was supported by the Russian Foundation for Basic Research (Grant No. 16-02-00073), the Administration of Krasnoyarsk Kray and the Krasnoyarsk Kray Foundation for Scientific and Technical Progress (Grant No. 16-42-240435), and the complex program No. II.2P of the Siberian Branch of the Russian Academy of Sciences (Grant No. 0356-2015-0405).
Предметные рубрики: T-J MODEL
LONG-RANGE-ORDER
POLARON
CUO2
EXCITATIONS
LATTICE
WAVE
Ключевые слова (''Своб.индексиров.''): high-temperature conductor--spin-fermion model--magnetic susceptibility--spin polaron
Аннотация: Using the method of diagram techniques for the spin and Fermi operators in the framework of the SU(2)-invariant spin-fermion model of the electron structure of the CuO2plane of copper oxides, we obtain an exact representation of the Matsubara Green’s function D⊥(k, iω m ) of the subsystem of localized spins. This representation includes the Larkin mass operator ΣL(k, iω m ) and the strength and polarization operators P(k, iω m ) and Π(k, iω m ). The calculation in the one-loop approximation of the mass and strength operators for the Heisenberg spin system in the quantum spin-liquid state allows writing the Green’s function D⊥(k, iω m ) explicitly and establishing a relation to the result of Shimahara and Takada. An essential point in the developed approach is taking the spin-polaron nature of the Fermi quasiparticles in the spin-fermion model into account in finding the contribution of oxygen holes to the spin response in terms of the polarization operator Π(k, iω m ).
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Manifestation of spin-charge fluctuations in the spectral and thermodynamic properties of quasi-two-dimensional rare-earth intermetallic compounds
Коллективы : RFBR [16-02-00073-a, 15-42-04372-r-Siberia-a]; Government of the Krasnoyarsk Region; Regional Science Foundation [07/16]; Integrated program II.2P of SB RAS [0358-2015-0002]; Presidential scholarships for young PhDs [SP-1370.2015.5]
Место публикации : Low Temp. Phys.: American Institute of Physics, 2017. - Vol. 43, Is. 2. - P.191-199. - ISSN 1063-777X, DOI 10.1063/1.4977211. - ISSN 1090-6517(eISSN)
Примечания : Cited References:35. - This work was supported by RFBR (Grants Nos. 16-02-00073-a and 15-42-04372-r-Siberia-a), the Government of the Krasnoyarsk Region and the Regional Science Foundation (Ext. Agreement No. 07/16), as well as the Integrated program II.2P of SB RAS (Project No. 0358-2015-0002). One of the authors (A.O.Z.) acknowledges the support by the Presidential scholarships for young PhDs (SP-1370.2015.5).
Предметные рубрики: PERIODIC ANDERSON MODEL
INTERMEDIATE-VALENCE COMPOUNDS
MAGNETIC PHASE-DIAGRAM
HEAVY
SUSCEPTIBILITY
APPROXIMATION
ANTIFERROMAGNETISM
SUPERCONDUCTIVITY
LATTICE
METALS
Аннотация: In the framework of the modified periodic Anderson model with exchange interaction in the subsystem of localized states, it is shown that spin-charge fluctuations in quasi-two-dimensional intermetallic compounds with rare-earth ions in the mixed valence state significantly affect both the spectrum of magnetic excitations and the conditions at which the antiferromagnetic phase is realized. The spectral characteristics of the phase were obtained by the method of the diagram technique for Hubbard operators in the one-loop approximation, which allows to account for the spincharge fluctuation contributions to the components of the mass and the force operators. The developed theory allowed to quantitatively describe the pressure dependence of the Neel temperature observed in a quasi-two-dimensional antiferromagnetic heavy-fermion intermetallic compound CeRhIn5. Published by AIP Publishing.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : On the concentration dependence of wings of spectra of spin correlation functions of diluted heisenberg paramagnets
Место публикации : JETP Letters. - 2016. - Vol. 103, Is. 11. - P.687-691. - ISSN 0021-3640, DOI 10.1134/S0021364016110138. - ISSN 1090-6487(eISSN)
Примечания : Cited References:26
Предметные рубрики: HIGH-TEMPERATURES
AUTOCORRELATION FUNCTION
SINGULAR POINT
SYSTEMS
TIME
COORDINATE
LATTICE
Аннотация: Singular points of the autocorrelation function on the imaginary time axis that is averaged over the location of spins in the magnetically dilute spin lattice with isotropic spin-spin interaction at a high temperature have been studied. For the autocorrelation function in the approximation of the self-consistent fluctuating local field, nonlinear integral equations have been proposed which reflect the separation of the inhomogeneous spin systems into close spins and other spins. The coordinates of the nearest singular points have been determined in terms of the radius of convergence of the expansion in powers of time, the coefficients of which have been calculated from recurrence equations. It has been shown that the coordinates of singular points and, consequently, the wings of the autocorrelation function spectrum at strong magnetic dilution are determined by the modulation of the local field by the nearest pairs of spins leading to its logarithmic concentration dependence.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Quantum and classical correlations in the solid-state NMR free induction decay
Место публикации : Appl. Magn. Reson.: Springer, 2014. - Vol. 45, Is. 11. - P.1169-1177. - ISSN 0937-9347, DOI 10.1007/s00723-014-0562-2. - ISSN 1613-7507
Примечания : Cited References: 16
Предметные рубрики: LATTICE
SPINS
Аннотация: The free induction decay (FID) of the transverse magnetization in a dipolar-coupled rigid lattice is a fundamental problem in magnetic resonance and in the theory of many-body systems. As it was shown earlier the FID shapes for the systems of classical magnetic moments and for quantum nuclear spin ones coincide if there are many nearly equivalent nearest neighbors n in a solid lattice. In this paper, we reduce a multispin density matrix of above system to a two-spin matrix. Then we obtain analytic expressions for the mutual information and the quantum and classical parts of correlations at the arbitrary spin quantum number S, in the high-temperature approximation. The time dependence of these functions is expressed via the derivative of the FID shape. To extract classical correlations for S 1/2 we provide generalized POVM measurement (positive-operator-valued measure) using the basis of spin coherent states. We show that in every pair of spins the portion of quantum correlations changes from 1/2 to 1/(S + 1) when S is growing up, and quantum properties disappear completely only if S → ∞.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Romanova O. B., Har'kov A. M., Balaev D. A., Gorev M. V., Vorotynov A. M., Sokolov V. V., Pichugin A.
Заглавие : Metal–semiconductor transition in SmxMn1−xS solid solutions
Место публикации : Phys. Status Solidi B. - 2012. - Vol. 249, Is. 4. - P.812-817. - ISSN 0370-1972, DOI 10.1002/pssb.201147327
Примечания : Cited References: 27. - This study was supported by the Russian Foundation for Basic Research project No 09-02-00554_a; No 09-02-92001-NNS_a; No 11-02-98018 r_sibir_a; ADTP "Development of scientific potential of the higher school" No. 2.1.1/11763.
Предметные рубрики: Magnetic-properties
Phase-transition
SmS
Valence
Pressure
Crystal
Lattice
CeRhSb
Ключевые слова (''Своб.индексиров.''): kondo effect--metal-semiconductor transition--semiconductors--variable-valence elements
Аннотация: The electrical resistivity of the SmxMn1−xS (0.15 ≤ x ≤ 0.25) solid solutions in the temperature range of 80–300 K was measured. Minimum and maximum in the temperature dependence of the resistivity were found, respectively, at T = 220 K for x = 0.15 and at T = 100 K for x = 0.2 compounds. This behavior is explained from the result of the mobility-edge movement, the disorder being due to elastic deformation and spin density fluctuations with short-range order. Metal–semiconductor phase transition versus concentration at xc = 0.25 is observed. Resistivity is described by scattering electrons with acoustic phonon mode and with localized manganese spin. From the thermal expansion coefficient the compression of the lattice below the Néel temperature for Sm0.2Mn0.8S is found.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kolovsky A. R., Link J., Wimberger S.
Заглавие : Energetically constrained co-tunneling of cold atoms
Место публикации : New J. Phys.: IOP Publishing Ltd, 2012. - Vol. 14. - Ст.75002. - ISSN 1367-2630, DOI 10.1088/1367-2630/14/7/075002
Примечания : 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.
Предметные 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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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : On the implementation of the coexistence phase of antiferromagnetism and superconductivity in heavy-fermion intermetallides
Место публикации : JETP Letters. - 2012. - Vol. 95, Is. 7. - P.350-356. - ISSN 0021-3640, DOI 10.1134/S0021364012070089
Примечания : Cited References: 29. - This work was supported by the Presidium of the Russian Academy of Sciences (program "Quantum Mesoscopic and Disordered Structures"), the Russian Foundation for Basic Research (project nos. 10-02-00251 and 11-02-98007-Siberia), and the Ministry of Education and Science of the Russian Federation (federal program "Human Capital for Science and Education in Innovative Russia" for 2009-2013).
Предметные рубрики: QUANTUM-CRITICAL-POINT
CRITICAL PRESSURE
CERHIN5
LATTICE
Аннотация: The region of the state diagram in which the pressure-induced quantum phase transition occurs with the destruction of the antiferromagnetic ordering and the appearance of the superconductivity has been described within the periodic Anderson model. It has been shown that a microscopically homogeneous coexistence phase of antiferromagnetism and superconductivity is implemented in the vicinity of the critical point, which was experimentally found in the heavy-fermion compound CeRhIn5. In this region, the pressure increase is accompanied by the experimentally observed strong growth of the effective fermion mass.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M.
Заглавие : EFFECTIVE INTERACTIONS IN THE PERIODIC ANDERSON MODEL IN THE REGIME OF MIXED VALENCY WITH STRONG CORRELATIONS
Коллективы :
Разночтения заглавия :авие SCOPUS: Effective interactions in the periodic Anderson model in the regime of mixed valency with strong correlations
Место публикации : Theor. Math. Phys.: SPRINGER, 2008. - Vol. 157, Is. 2. - P1565-1576. - ISSN 0040-5779, DOI 10.1007/s11232-008-0130-8
Примечания : 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.
Предметные рубрики: LATTICE
Ключевые слова (''Своб.индексиров.''): 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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