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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A.
Заглавие : A simple metal-insulator criterion for the doped Mott-Hubbard materials
Коллективы : RFBR [13-02-01395, 14-02-00186, Nsh-28862014.2]
Место публикации : Solid State Commun.: PERGAMON-ELSEVIER SCIENCE LTD, 2015. - Vol. 208. - P.11-14. - ISSN 0038, DOI 10.1016/j.ssc.2015.02.014. - ISSN 18792766(eISSN)
Примечания : Cited References:19. - We acknowledge with pleasure discussions with Igor S. Sandalov during the course of this work. This work was supported by RFBR Grant nos. 13-02-01395, 14-02-00186, and Nsh-28862014.2.
Предметные рубрики: COOPER PAIRS
Bi2Sr2CaCu2O8+DELTA
Ключевые слова (''Своб.индексиров.''): doped mott-hubbard materials--metal-insulator transition--first removal--electron states
Аннотация: A simple metal-insulator criterion for doped Mott-Hubbard materials has been derived, Its readings are closely related to the orbital and spin nature of the ground states of the unit cell. The available criterion readings (metal or insulator) in the paramagnetic phase reveal the possibility of the insulator state of doped materials with the forbidden first removal electron states. According to its physical meaning, the result is similar to the Wilson's criterion in itinerant electron systems. The application of the criterion to high-T-c cuprates is discussed. (C) 2015 Elsevier Ltd. All rights reserved.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Gavrichkov V. A.
Заглавие : A simple metal-insulator criterion for the doped Mott-Hubbard materials
Коллективы : School and Workshop on Strongly Correlated Electronic Systems - Novel Materials and Novel Theories, International Centre for Theoretical Physics
Место публикации : School and Workshop on Strongly Correlated Electronic Systems - Novel Materials and Novel Theories. - 2015
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GORYACHEV E. G.
Заглавие : A VARIATIONAL APPROACH TO THE 3-BODY PROBLEM IN THE HUBBARD-MODEL - EXACT RESULT
Место публикации : Phys. Lett. A: ELSEVIER SCIENCE BV, 1992. - Vol. 166, Is. 2. - P148-152. - ISSN 0375-9601, DOI 10.1016/0375-9601(92)90551-V
Примечания : Cited References: 7
Аннотация: A well-defined method for linearizing the many-body equation of motion in statistical mechanics is proposed. The one-particle retarded Green function for the special case of a single reversed spin in an otherwise fully aligned band is obtained. We prove that the results for the Green function coincide independently of the initial (unperturbed) state we have started with, that is, the band energy limit E(k) = SIGMA(h)b(h)e(ikh) or the two-level atomic limit (E0, E0 + U). This strong result is valid for any parameters of the Hamiltonian and electron concentration of [F\n up\F]. In the nontrivial limited case (U=infinity) the obtained Green function coincides with the exact result of Igarashi, Ruckenstein and Schmitt-Rink based on the solution of the Faddeev equations.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Valkov V. V.
Заглавие : Anomalous resistivity and superconductivity in the two-band Hubbard model with one narrow band (Review)
Место публикации : Low Temp. Phys. - 2011. - Vol. 37, Is. 1. - P.69-82. - ISSN 1063-777X, DOI 10.1063/1.3552118; \b Физика низких температур
Примечания : Cited References: 62. - We thank A.S. Alexandrov, A.F. Andreev, M.A. Baranov, Yu. Bichkov, A.V. Chubukov, D.V. Efremov, A.S. Hewson, K.A. Kikoin, F.V. Kusmartsev, P. Nozieres, T.M. Rice, A.O. Sboychakov, P. Thalmeer, C.M. Varma, D. Vollhardt, P. Woelfle, A. Yaresko and, especially, P. Fulde, Yu. Kagan, K.I. Kugel, and N.V. Prokof'ev for many simulating discussions on this subject and acknowledge the financial support of RFBR grants # 08-02-00224 and 08-02-00212. M.Yu.K. is also grateful to the Leverhulme trust for a grant to visit Loughborough University, where this work was completed.
Предметные рубрики: FERMI-LIQUID BEHAVIOR
MAGNETIC-ALLOYS
HEAVY
DENSITY
SYSTEMS
STATE
UPT3
MECHANISM
PARTICLE
VALENCE
Аннотация: We search for marginal Fermi-liquid behavior in the two-band Hubbard model with one narrow band. We consider the limit of low electron densities in the bands and strong intraband and interband Hubbard interactions. We analyze the influence of electron-polaron effects and other mechanisms for mass-enhancement (related to the momentum dependence of the self-energies) on the effective mass and scattering times of light and heavy components in the clean case (electron-electron scattering and no impurities). We find a tendency towards phase separation (towards negative partial compressibility of heavy particles) in the 3D case with a large mismatch between the densities of heavy and light bands in the strong coupling limit. We also find that for low temperatures and equal densities, the resistivity in a homogeneous state R(T) proportional to T-2 behaves as a Fermi-liquid in both 3D and 2D. For temperatures greater than the effective bandwidth for heavy electrons T W-h*, the coherence of the heavy component breaks down completely. The heavy particles move diffusively in the surrounding light particles. At the same time, light particles scatter on heavy particles as if on immobile (static) impurities. Under these conditions, the heavy component is marginal, while the light component is not. The resistivity approaches saturation for T W-h* in the 3D case. In 2D the resistivity has a maximum and a localization tail owing to weak-localization corrections of the Altshuler-Aronov type. This behavior of resistivity in 3D could be relevant for some uranium-based heavy-fermion compounds such as UNi2Al3 and in 2D, for some other mixed-valence compounds, possibly including layered manganites. We also consider briefly the superconductive (SC) instability in this model. The leading instability tends to p-wave pairing and is governed by an enhanced Kohn-Luttinger mechanism for SC at low electron densities. The critical temperature corresponds to the pairing of heavy electrons via polarization of the light electrons in 2D. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552118]
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M.Yu., Val'kov V. V.
Заглавие : Anomalous resistivity and the electron-polaron effect in the two- band Hubbard model with one narrow band
Место публикации : arXiv. - 2011. - Ст.1111.3135
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Val'kov V. V.
Заглавие : Anomalous resistivity and the electron-polaron effect in the two-band hubbard model with one narrow band
Место публикации : J. Supercond. Nov. Magn.: SPRINGER, 2012. - Vol. 25, Is. 5. - P.1379-1382. - ISSN 1557-1939, DOI 10.1007/s10948-012-1523-3
Примечания : Cited References: 28. - We are grateful to P. Fulde, Yu. Kagan, K. I. Kugel, N.V. Prokof'ev, P. Nozieres, and C. M. Varma for the numerous stimulating discussions. We acknowledge financial support of the RFBR Grant No. 11-02-00741.
Предметные рубрики: FERMI GAS
SUPERCONDUCTIVITY
SUPERFLUIDITY
TEMPERATURE
REPULSION
SYSTEMS
Ключевые слова (''Своб.индексиров.''): electron-polaron effect--two-band hubbard model--marginality--anomalous resistivity
Аннотация: We search for anomalous normal and superconductive behavior in the two-band Hubbard model with one narrow band. We analyze the influence of the electron–polaron effect and the Altshuler–Aronov effect on effective mass enhancement and scattering times of heavy and light components in the clean case. We find anomalous behavior of resistivity at high temperatures TW∗hT W_{h}. *} both in 3D and 2D situations. The SC instability in the model is governed by an enhanced Kohn–Luttinger effect for p-wave pairing of heavy electrons via polarization of light electrons.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Yu., Val'kov V. V.
Заглавие : Anomalous Resistivity and the Origin of Heavy Mass in the Two-Band Hubbard Model with One Narrow Band
Место публикации : J. Exp. Theor. Phys. - NEW YORK: PLEIADES PUBLISHING INC, 2011. - Vol. 113, Is. 1. - С. 156-171. - JUL. - ISSN 1063-7761, DOI 10.1134/S1063776111060021. - ISSN 1090-6509
Примечания : Cited Reference Count: 87. - RFBRRussian Foundation for Basic Research (RFBR) [08-02-00224, 08-02-00212]; Leverhulme trustLeverhulme Trust; CNRSCentre National de la Recherche Scientifique (CNRS)European Commission [236694], We are grateful to A. S. Alexandrov, A. F. Andreev, A. F. Barabanov, M. A. Baranov, Yu. Bychkov, A. V. Chubukov, D. V. Efremov, P. Fulde, A. S. Hewson, Yu. Kagan, K. A. Kikoin, K. I. Kugel, F. V. Kusmartsev, M. Mezard, Yu. E. Lozovik, P. Nozieres, N. V. Prokof'ev, A. L. Rakhmanov, T. M. Rice, A. O. Sboychakov, G. V. Shlyapnikov, P. Thalmeyer, C. M. Varma, D. Vollhardt, P. Woelfle, and A. Yaresko for the numerous simulating discussions on this subject and acknowledge financial support of the RFBR grants nos. 08-02-00224, 08-02-00212. M. Yu. K. is also grateful to Loughborough University (UK) and LPTMS (Orsay, France) for the hospitality during the final stage of this work and acknowledges financial support from the Leverhulme trust and CNRS (contract no. 236694).
Предметные рубрики: Physics, Multidisciplinary
Аннотация: We search for marginal Fermi-liquid behavior [1] in the two-band Hubbard model with one narrow band. We consider the limit of low electron densities in the bands and strong intraband and interband Hubbard interactions. We analyze the influence of electron polaron effect [2] and other mechanisms of mass enhancement (related to momentum dependence of the self-energies) on the effective mass and scattering times of light and heavy components in the clean case (electron-electron scattering and no impurities). We find the tendency towards phase separation (towards negative partial compressibility of heavy particles) in the 3D case for a large mismatch between the densities of heavy and light bands in the strong-coupling limit. We also observe that for low temperatures and equal densities, the homogeneous state resistivity R(T) similar to T-2 behaves in a Fermi-liquid fashion in both 3D and 2D cases. For temperatures higher than the effective bandwidth for heavy electrons T W-h*, the coherent behavior of the heavy component is totally destroyed. The heavy particles move diffusively in the surrounding of light particles. At the same time, the light particles scatter on the heavy ones as if on immobile (static) impurities. In this regime, the heavy component is marginal, while the light one is not. The resistivity saturates for T W-h* in the 3D case. In 2D, the resistivity has a maximum and a localization tail due to weak-localization corrections of the Altshuler-Aronov type [3]. Such behavior of resistivity could be relevant for some uranium-based heavy-fermion compounds like UNi2Al3 in 3D and for some other mixed-valence compounds possibly including layered manganites in 2D. We also briefly consider the superconductive (SC) instability in the model. The leading instability is towards the p-wave pairing and is governed by the enhanced Kohn-Luttinger [4] mechanism of SC at low electron density. The critical temperature corresponds to the pairing of heavy electrons via polarization of the light ones in 2D.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Mitskan V. A., Korovushkin M. M.
Заглавие : Anomalous superconductivity and superfluidity in repulsive fermion systems
Место публикации : Phys. Usp.: Turpion, 2015. - Vol. 58, Is. 8. - P.733-761. - ISSN 10637869 (ISSN), DOI 10.3367/UFNe.0185.201508a.0785
Примечания : Cited References: 369. - We are grateful to M A Baranov, A V Chubukov, D V Efremov, M V Feigel'man, V V Kabanov, K I Kugel', M S Marienko, N M Plakida, N V Prokorev, A Ya Tzalenchuk, and V V Val'kov for the fruitful discussions and constant attention to our work. The work was supported by the Russian Foundation for Basic Research (project nos. 14-02-00058 and 14-02-31237). M Yu K thanks the Program of Basic Research of the National Research University Higher School of Economics for support. The work of MM K was supported by grant of the President of the Russian Federation (SP-1361.2015.1) and the Dinasty Foundation
Предметные рубрики: HEXAGONAL BORON-NITRIDE
SCANNING-TUNNELING-MICROSCOPY
2-DIMENSIONAL HUBBARD-MODEL
HIGH-TC SUPERCONDUCTIVITY
ELECTRON-ENERGY SPECTRUM
P-WAVE SUPERCONDUCTIVITY
DOUBLE-LAYER GRAPHENE
2D KONDO-LATTICE
GROUND-STATE
TRANSITION-TEMPERATURE
Ключевые слова (''Своб.индексиров.''): anomalous superconductivity--kohn-luttinger mechanism--superfluidity--repulsive fermi gas--hubbard and t-jmodel--shubin vonsovsky model--graphene monolayer--graphene bilayer
Аннотация: We discuss the mechanisms of unconventional superconductivity and superfluidity in 3D and 2D fermionic systems with purely repulsive interaction at low densities. We construct phase diagrams of these systems and find the areas of the superconducting state in free space, as well as on the lattice in the framework of the Fermi-gas model with hard-core repulsion, the Hubbard model, the Shubin-Vonsovsky model, and the t-J model. We demonstrate that the critical superconducting temperature can be greatly increased in the spin-polarized case or in a two-band situation already at low densities. The proposed theory is based on the Kohn-Luttinger mechanism or its generalizations and explains or predicts anomalous p-, d-, and f-wave pairing in various materials, such as high-temperature superconductors, the idealized monolayer and bilayer of doped graphene, heavy-fermion systems, layered organic superconductors, superfluid 3He, spin-polarized 3He mixtures in 4He, ultracold quantum gases in magnetic traps, and optical lattices.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Sidorov K. A., Shneyder E. I.
Заглавие : Anomalous thermodynamics of the doped Mott-Hubbard insulators
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 2. - P299-302. - ISSN 1063-7834, DOI 10.1134/S1063783411020247
Примечания : Cited References: 6. - This study was supported by the Russian Foundation for Basic Research (project no. 09-02-00127), the Branch of the Physical Sciences of the Russian Academy of Sciences (program nos. 2 and 3), grant no. MK-1683.2010.2, and by the Federal Target Program "Personnel" (project NK-589 P).
Предметные рубрики: T-J MODEL
SPECTRUM
Аннотация: The concentration dependence of the entropy of doped Mott-Hubbard insulators has been considered within the t-J model. It has been shown that a change in the type and statistics of charge carriers as compared to the Fermi gas leads to a radical change in the entropy s, in particular, to the giant growth of the entropy upon doping. The quantity a,s/a,x a parts per thousand k (B) is approximately consistent with the experimental data for HTSC cuprates in the pseudogap phase.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin U., Sandalov I., Eriksson O., Johansson B.
Заглавие : Are there two types of f-electrons in Pr-metal?
Коллективы : International Conference on Strongly Correlated Electron Systems
Место публикации : Physica B. - 1999. - Vol. 259-61. - P.231-232. - ISSN 0921-4526, DOI 10.1016/S0921-4526(98)00790-X
Примечания : Cited References: 1
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): band calculations--hubbard model--f-electrons
Аннотация: We show that in order to properly describe the bonding properties of strongly correlated systems, here demonstrated for praseodymium metal, it is necessary to split the f-electron system into two parts. Using perturbation theory from the atomic limit we show that LDA-based calculations with f-electrons in the core can be considered as the limit of an infinite Hubbard U. Then, the correction to the total energy proportional to 1/U makes the upper f(2)--f(3) intra-atomic transitions (IT) important. Mixing interaction and f-f-hopping delocalize these IT and some of them become populated. These IT give an additional contribution to the cohesive energy. This gain in energy is the reason for the separation of the f-electron system into localized (with reduced spectral weight) and delocalized ones. (C) 1999 Elsevier Science B.V. All rights reserved.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kolovsky A. R., Korsch H. J., Graefe E. M.
Заглавие : Bloch oscillations of Bose-Einstein condensates: Quantum counterpart of dynamical instability
Место публикации : Phys. Rev. A. - 2009. - Vol. 80, Is. 2. - ISSN 1050-2947, DOI 10.1103/PhysRevA.80.023617
Примечания : Cited Reference Count: 35. - Гранты: We thank D. Witthaut and F. Trimborn for valuable comments. Support from the Deutsche Forschungsgemeinschaft via the Graduiertenkolleg "Nichtlineare Optik und Ultrakurzzeitphysik" is gratefully acknowledged.Финансирующая организация: Deutsche Forschungsgemeinschaft
Предметные рубрики: OPTICAL LATTICE
ATOMS
Ключевые слова (''Своб.индексиров.''): bloch dynamics--bloch oscillations--bogoliubov--bose-einstein condensates--chaotic dynamics--cold atoms--decoherence--dinger equation--dynamical instabilities--equipartition--hubbard--mean-field--optical lattices--quantum counterpart--quasi-one-dimensional--quasimomentum--bose-einstein condensation--hamiltonians--nonlinear equations--steam condensers--stability
Аннотация: We study the Bloch dynamics of a quasi-one-dimensional Bose-Einstein condensate of cold atoms in a tilted optical lattice modeled by a Hamiltonian of Bose-Hubbard type. The corresponding mean-field system described by a discrete nonlinear Schrodinger equation can exhibit dynamical (or modulation) instability due to chaotic dynamics and equipartition over the quasimomentum modes. It is shown that these phenomena are related to Bogoliubov's depletion of the Bose-Einstein condensate and a decoherence of the condensate in the many-particle description. Three types of dynamics are distinguished: (i) decaying oscillations in the region of dynamical instability and (ii) persisting Bloch oscillations or (iii) periodic decay and revivals in the region of stability.
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12.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Kolovsky A. R.
Заглавие : Bose-Hubbard Hamiltonian: Quantum Chaos Approach
Коллективы : Workshop On Bose-Einstein Condensation and Quantum Chaos
Место публикации : Worksh. Bose-Einstein condens. and quant. chaos. - 2015
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kolovsky A. R.
Заглавие : Bose-Hubbard Hamiltonian: Quantum chaos approach
Место публикации : Int. J. Mod. Phys. B: World Scientific Publishing, 2016. - Vol. 30, Is. 10. - Ст.1630009. - ISSN 0217-9792, DOI 10.1142/S0217979216300097. - ISSN 1793-6578(eISSN)
Примечания : Cited References:42
Предметные рубрики: Optical lattice
Dynamics
Atoms
States
Model
Ключевые слова (''Своб.индексиров.''): cold atoms in optical lattices--quantum transport--nonlinear dynamics and chaos
Аннотация: We discuss applications of the theory of quantum chaos to one of the paradigm models of many-body quantum physics - the Bose-Hubbard (BH) model, which describes, in particular, interacting ultracold Bose atoms in an optical lattice. After preliminary, pure quantum analysis of the system we introduce the classical counterpart of the BH model and the governing semiclassical equations of motion. We analyze these equations for the problem of Bloch oscillations (BOs) of cold atoms where a number of experimental results are available. The paper is written for nonexperts and can be viewed as an introduction to the field.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Nikolaev S. V.
Заглавие : Calculation of the Fermi Surface with Complex Topology from Norm-Conserving Cluster Perturbation Theory for Doping Dependent Electronic Structure of the Hubbard Model
Место публикации : JETP Letters. - 2011. - Vol. 93, Is. 9. - P.517-520. - ISSN 0021-3640, DOI 10.1134/S0021364011090116
Примечания : Cited References: 27. - This work was supported by the Presidium of the Russian Academy of Sciences (program no. 18.7); the Russian Foundation for Basic Research (project nos. 09-02-00127, 10-02-90725-mob_st); Siberian Branch, Russian Academy of Sciences (Integration Project no. N40); and the Ministry of Education and Sciences of the Russian Federation (state contract no. P891, Program "Kadry").
Предметные рубрики: QUANTUM OSCILLATIONS
SUPERCONDUCTORS
EVOLUTION
Аннотация: The results of recently developed norm-conserving cluster perturbation theory for doping dependent electronic structure of the Hubbard model are reported. We have found that the momentum distribution of the spectral weight strongly depends on the broadening value delta. At delta = 0.1t, we reproduce the angle-resolved photoemission spectroscopy data, while at delta = 0.01t we obtain two quantum phase transitions. DOI: 10.1134/S0021364011090116
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15.

Вид документа : Статья из сборника (выпуск продолж. издания)
Шифр издания :
Автор(ы) : Bychek A. A., Muraev P. S., Maksimov D. N., Bulgakov E. N., Kolovsky A. R.
Заглавие : Chaotic and regular dynamics in the three-site Bose-Hubbard model
Коллективы : International Conference on Quantum Technologies
Место публикации : AIP Conf. Proc. - 2020. - Vol. 2241. - Ст.020007. - DOI 10.1063/5.0011540
Примечания : Cited References: 30. - This work has been supported through Russian Science Foundation Grant N19-12-00167
Аннотация: We analyze the energy spectrum of the three-site Bose-Hubbard model. It is shown that this spectrum is a mixture of the regular and irregular spectra associated with the regular and chaotic components of the classical Bose-Hubbard model. We find relative volumes of these components by using the pseudoclassical approach. Substituting these values in the Berry-Robnik distribution for the level spacing statistics we obtain good agreement with the numerical data.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kim J., Shvyd'ko Y., Ovchinnikov S. G.
Заглавие : Charge transfer and Mott-Hubbard excitations in FeBO3: An Fe K-edge resonant inelastic x-ray scattering study
Разночтения заглавия :авие SCOPUS: Charge transfer and Mott-Hubbard excitations in FeBO 3: An Fe K-edge resonant inelastic x-ray scattering study
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2011. - Vol. 83, Is. 23. - Ст.235109. - ISSN 1098-0121, DOI 10.1103/PhysRevB.83.235109
Примечания : Cited References: 67. - Yu.Sh. acknowledges the long-standing effort of his colleagues from the IXS Collaborative Design Team in building MERIX instrument at the XOR-IXS 30-ID beamline at the APS, in particular, J. Hill, S. Coburn (BNL), C. Burns (WMU), E. Alp, T. Toellner, and H. Sinn (APS). He is also indebted to R. Khachatryan (APS), M. Wieczorek (APS), and A. Said (APS) for the help in manufacturing the Ge(620) analyzer. P. Siddons (BNL) is acknowledged for building the microstrip detector for the MERIX spectrometer. The help of the XOR-IXS 30-ID beamline personnel at the Advanced Photon Source: T. Roberts, A. Said, and M. Upton are greatly appreciated. Use of the Advanced Photon Source was supported by the US DOE, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. S.O. acknowledges Russian Academy of Science Physical Department program 5.7 "Strongly correlated electrons," RFFI Grant No. 09-02-00171, RFFI Grant No. 10-02-00251, and the Siberian-Ural integration Project No. 40.
Предметные рубрики: TRANSITION-METAL COMPOUNDS
ELECTRONIC-STRUCTURE
OPTICAL-PROPERTIES
ABSORPTION-SPECTRA
EMISSION SPECTRA
FERROMAGNET
DEPENDENCE
COMPLEXES
RAMAN
Аннотация: Momentum-resolved resonant inelastic x-ray scattering (RIXS) spectroscopy has been carried out successfully at the Fe K-edge for the first time. The RIXS spectra of a FeBO3 single crystal reveal a wealth of information on similar or equal to 1-10 eV electronic excitations. The IXS signal resonates when the incident photon energy approaches the pre-edge (1s-3d) and the main-edge (1s-4p) of the Fe K-edge absorption spectrum. The RIXS spectra measured at the pre-edge and the main-edge show quantitatively different dependences on the incident photon energy, momentum transfer, photon polarization, and temperature. We present a multielectron analysis of the Mott-Hubbard (MH) and charge transfer (CT) excitations, and calculate their energies. Electronic excitations observed in the pre-edge and main-edge RIXS spectra are interpreted as MH and CT excitations, respectively. We propose the electronic structure around the chemical potential in FeBO3 based on the experimental data.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Cluster perturbation theory in Hubbard model exactly taking into account the short-range magnetic order in 2 x 2 cluster
Коллективы :
Разночтения заглавия :авие SCOPUS: Cluster perturbation theory in Hubbard model exactly taking into account the short-range magnetic order in 2 × 2 cluster
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 111, Is. 4. - P635-644. - ISSN 1063-7761, DOI 10.1134/S1063776110100146
Примечания : Cited References: 23. - The authors thank V. V. Val'kov for fruitful discussions of this work. This research was supported financially by the Russian Foundation for Basic Research (project nos. 09-02-90723-mob_st and 09-02-00127) and by program no. 5.7 of the Presidium of the Russian Academy of Sciences and integration project no. 40 of the Siberian Branch and Ural Division of the Russian Academy of Sciences.
Предметные рубрики: INFINITE DIMENSIONS
SYSTEMS
STATE
Ключевые слова (''Своб.индексиров.''): antiferromagnetic orders--characteristic energy--cluster perturbation theories--coulomb repulsions--density of state--dynamic mean field theories--eigenvalue problem--exact diagonalization--excited levels--finite temperatures--half-filling--hubbard--metal insulator transition temperature--nearest neighbors--numerical solution--pseudo-gap--quasiparticle spectrum--shadow zone--short-range magnetic orders--temperature evolution--zero temperatures--antiferromagnetism--eigenvalues and eigenfunctions--fermi level--hubbard model--mean field theory--metal insulator boundaries--perturbation techniques--semiconductor insulator boundaries--statistical mechanics--metal insulator transition
Аннотация: The cluster perturbation theory is presented in the 2D Hubbard model constructed using X operators in the Hubbard-I approximation. The short-range magnetic order is taken into account by dividing the entire lattice into individual 2 x 2 clusters and solving the eigenvalue problem in an individual cluster using exact diagonalization taking into account all excited levels. The case of half-filling taking into account jumps between nearest neighbors is considered. As a result of numerical solution, a shadow zone is discovered in the quasiparticle spectrum. It is also found that a gap in the density of states in the quasiparticle spectrum at zero temperature exists for indefinitely small values of Coulomb repulsion parameter U and increases with this parameter. It is found that the presence of this gap in the spectrum is due to the formation of a short-range antiferromagnetic order. An analysis of the temperature evolution of the density of states shows that the metal-insulator transition occurs continuously. The existence of two characteristic energy scales at finite temperatures is demonstrated, the larger scale is associated with the formation of a pseudogap in the vicinity of the Fermi level, and the smaller scale is associated with the metal-insulator transition temperature. A peak in the density of states at the Fermi level, which is predicted in the dynamic mean field theory in the vicinity of the metal-insulator transition, is not observed.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krinitsyn A., Nikolaev S., Ovchinnikov S. G.
Заглавие : Cluster size and shape effect on the electronic structure of the Hubbard model within the norm-conserving cluster perturbation theory
Коллективы : Siberian Federal University [F-11]; Presidium of RAS Program [20.7]; [NSh-1044.2012.2]; [MK-1168.2012.2]
Место публикации : J. Supercond. Nov. Magn.: Springer, 2014. - Vol. 27, Is. 4. - P.955-963. - ISSN 1557-1939, DOI 10.1007/s10948-013-2418-7. - ISSN 1557-1947
Примечания : Cited References: 59. - This work was supported by Grants NSh-1044.2012.2 and MK-1168.2012.2, Siberian Federal University: Grant F-11, and the Presidium of RAS Program 20.7.
Предметные рубрики: NARROW ENERGY-BANDS
CUPRATE SUPERCONDUCTORS
PHOTOEMISSION SPECTRA
PSEUDOGAP
ANTIFERROMAGNET
EXCITATIONS
EVOLUTION
SYSTEMS
PHASE
STATE
Ключевые слова (''Своб.индексиров.''): cluster perturbation theory--hubbard model--strong correlations--density of states--fermi surface
Аннотация: Within a new norm-conserving approach to the cluster perturbation theory (CPT) for the 2d Hubbard model we study the effect of the cluster size and shape on the electronic structure. We have compared two type of clusters, 4-cluster (2x2) and 5-cluster (cruciform of 5 atoms). With 4-cluster we can treat exactly the first and second neighbours correlations, C (1) and C (2). With 5-cluster the third neighbour correlations C (3) are also treated exactly. The band structure in the CPT with 4- and 5-clusters differs remarkably. The quasiparticle spectral weight map for 5-clusters is very similar to the Quantum Monte Carlo (QMC) and the variational CPT data. With increasing doping, small hole Fermi surface transforms into conventional Fermi-liquid type large Fermi surface through Lifshitz quantum phase transitions.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Coexistence of the chiral superconductivity and noncollinear magnetic order in the ensemble of Hubbard fermions on a triangular lattice
Место публикации : JETP Letters. - 2016. - Vol. 104, Is. 7. - P.483-488. - ISSN 00213640 (ISSN), DOI 10.1134/S0021364016190127
Примечания : Cited References: 24. - This work was supported by the Russian Foundation for Basic Research (project no. 16-02-00073-a), by the Government of Krasnoyarsk Krai (project no. 16-42-243069-r-mol-а), and by the Siberian Branch, Russian Academy of Sciences (project no. 0358-2015-0002, Complex Program II.2P). The work of A.O.Z. was supported by the Council of the President of the Russian Federation for State Support of Young Scientists and Leading Scientific Schools (project no. SP-1370.2015.5).
Аннотация: For the system of strongly correlated electrons on a triangular lattice, the possibility of coexisting superconductivity with the chiral order parameter and the 120°-type noncollinear spin ordering is demonstrated. The integral self-consistency equation for the superconducting order parameter is derived using the diagram technique for Hubbard operators taking into account the spin structure, exchange interaction within two coordination spheres, and intersite Coulomb repulsion. © 2016, Pleiades Publishing, Inc.
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20.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Comparison of electronic structure, magnetic mechanism, and symmetry of pairing in ruthenates and cuprates
Место публикации : Ruthenate and rutheno-cuprate materials: unconventional superconductivity, magnetism and quantum phase transitions. Ser. lecture notes in physics: Springer Verlag, 2002. - Vol. 603: International Conference on Ruthenate and Rutheno-Cuprate Materials (OCT 25-27, 2001, VIETRI SUL MARE, ITALY). - P.239-255. - ISBN 0075-8450. - ISBN 3-540-44275-8
Примечания : Cited References: 48
Предметные рубрики: METAL-INSULATOR-TRANSITION
SUPERCONDUCTOR SR2RUO4
LAYERED PEROVSKITE
BAND-STRUCTURE
CORRELATED ELECTRONS
MOTT TRANSITION
COPPER OXIDES
HUBBARD-MODEL
RUSR2GDCU2O8
CA2-XSRXRUO4
Аннотация: A generalized tight-binding (GTB) method is developed to calculate quasi-particle band structure with explicit account for strong electronic correlations. The GTB method combines exact diagonalization of the multi-orbital P-d model Hamiltonian within the unit cell and the perturbation theory in the Hubbard X-operators form for the inter-cell hopping and interactions. For undoped cuprates we obtain the valence band structure in excellent agreement with ARPES data, evolution of the band structure with doping with an in-gap state at small doping, impurity-like band at higher doping to optimally doped metal. The effective low-energy Hamiltonian has the form of singlet-triplet t-J model. For ruthenates the t-J-I model is proposed with both antiferromagnetic J and ferromagnetic I couplings. In the strong correlation limit, the mean-field theory of superconductivity results in d-wave singlet pairing mediated by J (cuprates) and p-wave triplet one mediated by I (ruthenates) with ratio T-c((d))/T-c((p)) similar to 100 due to the different symmetry of the gap. The competition of ferromagnetic and antiferromagnetic order in rutheno-cuprates is also discussed.
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