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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Кузьмин, Валерий Ипполитович, Николаев, Сергей Викторович
Заглавие : Исследование аномалий электронной дисперсии в модели Хаббарда, t-J- и t-J*-модели в рамках кластерной теории возмущений в представлении Х-операторов
Коллективы : Сибирский молодежный семинар по высокотемпературной сверхпроводимости и физике наноструктур – ОКНО 2014 (X; 13 - 14 ноября 2014 г.; Новосибирск)
Место публикации : Вестник НГУ. Физика. - 2015. - Т. 10, Вып. 1. - С. 50-56. - ISSN 1818-7994
Примечания : Библиогр.: 23. - Работа выполнена при финансовой поддержке Российского научного фонда (проект № 14-12-00061).
Ключевые слова (''Своб.индексиров.''): высокотемпературная сверхпроводимость--электронная структура купратов--высокоэнергетические кинки--кластерные теории--модель хаббарда--t-j-модель--high-temperature superconductivityory--electronic structure of cuprates--high-energy kinks--cluster perturbation theory--hubbard model--t-j-model
Аннотация: В рамках кластерной теории возмущений в представлении Х-операторов Хаббарда рассчитана энергетическая структура электронов в модели Хаббарда, t-J- и t-J *-модели с учетом уширения спектральных линий, соответствующего экспериментам по фотоэмиссионной спектроскопии с угловым разрешением. При энергиях порядка интеграла перескока t в полученных спектрах наблюдаются аномалии, схожие с высокоэнергетическими кинками, наблюдаемыми в экспериментах по фотоэмиссионной спектроскопии с угловым разрешением. Исследовано поведение высокоэнергетических аномалий электронной дисперсии при изменениях величины допирования и параметра кулоновского отталкивания. Проанализировано влияние трехцентровых коррелированных перескоков на результаты расчета.The electronic structure with the spectral line broadening corresponding to the angle-resolved photoemission spectroscopy resolution has been calculated for the Hubbard model, t-J and t-J * models within the norm-conserving cluster perturbation theory. The electronic dispersion anomalies similar to the high-energy kinks observed in the angle-resolved photoemission spectroscopy experiments are obtained at the energy scale of order of the hopping integral t. The doping dependence of the high-energy anomalies for different Coulomb repulsion values is discussed. The influence of the three-site correlated hopping on the results is analyzed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : VALKOV V. V., OVCHINNIKOV S. G.
Заглавие : HUBBARD OPERATORS AND SPIN-WAVE THEORY OF HEISENBERG MAGNETS WITH ARBITRARY SPIN
Место публикации : Theor. Math. Phys.: PLENUM PUBL CORP, 1982. - Vol. 50, Is. 3. - P306-313. - ISSN 0040-5779, DOI 10.1007/BF01016463
Примечания : Cited References: 32
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Golovnya A. A., Dzebisashvili D. M.
Заглавие : The role of anomalous strength operator in the high-T (c) superconductivity theory
Разночтения заглавия :авие SCOPUS: The role of anomalous strength operator in the high- Tc superconductivity theory
Место публикации : Physica B: ELSEVIER SCIENCE BV, 2006. - Vol. 378-80: International Conference on Strongly Correlated Electron Systems (SECES 05) (JUL 26-30, 2005, Vienna, AUSTRIA). - P465-466. - ISSN 0921-4526, DOI 10.1016/j.physb.2006.01.202
Примечания : Cited References: 3
Ключевые слова (''Своб.индексиров.''): superconductivity--t-j-model--superconductivity--t- j-model--approximation theory--frequencies--mathematical operators--numerical methods--superconducting transition temperature--superconductivity--hubbard operator--matsubara frequency--t- j-model--high temperature superconductors
Аннотация: The diagram series structure for Matsubara Green's functions in the Hubbard operators representation have been analyzed for the superconducting (SC) phase in the t-J-model. It has been found that the Hubbard operator diagram technique besides anomalous self-energy operator includes also anomalous strength operator (ASO). With account for ASO Gor'kov equations have been written. ASO are shown to be very essential when anomalous averages are calculated. The anomalous self-energy operator and ASO were derived in one-loop approximation. It has turned out that strength operator components depend oil Matsubara frequency. As a result the SC phase is described by infinite set of integral equations. When deriving the equation for transition temperature in SC phase with s- and d-order parameter symmetry this system has been solved exactly. On the basis of numerical calculations it has been found that the account for strength operator components has fully suppressed SC phase with s-order parameter symmetry in the t-J-model. (c) 2006 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M.
Заглавие : The electron energy spectrum and superconducting transition temperature of strongly correlated fermions with three-center interactions
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2005. - Vol. 100, Is. 3. - P608-616. - ISSN 1063-7761, DOI 10.1134/1.1901772
Примечания : Cited References: 29
Предметные рубрики: T-J MODEL
BAND HUBBARD-MODEL
VALENCE BOND STATE
RANGE-ORDER
SYSTEMS
WAVE
Ключевые слова (''Своб.индексиров.''): antiferromagnetic materials--approximation theory--fermions--ground state--hamiltonians--superconductivity--density of states--electron energy spectrum--strongly correlated fermions--superconducting phase--superconducting transition temperature
Аннотация: The renormalizations of the fermionic spectrum are considered within the framework of the t-J* model taking into account three-center interactions (H-(3)) and magnetic fluctuations. Self-consistent spin dynamics equations for strongly correlated fermions with three-center interactions were obtained to calculate quasi-spin correlators. A numerical self-consistent solution to a system of ten equations was obtained to show that, in the nearest-neighbor approximation, simultaneously including H-(3) and magnetic fluctuations at n n(1) (n(1) approximate to 0.72 for 2t/U = 0.25) caused qualitative changes in the structure of the energy spectrum. A new Van Hove singularity is then induced in the density of states, and an additional maximum appears in the T-c(n) concentration dependence of the temperature of the transition to the superconducting phase with order parameter symmetry of the d(x2-y2) type. (C) 2005 Pleiades Publishing, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Val’kova T. A., Mitskan V. A.
Заглавие : Superconducting phase with the (d + id) order parameter in an ensemble of Hubbard fermions on the triangular lattice
Место публикации : JETP Letters. - 2015. - Vol. 102, Is. 6. - P.361-366. - ISSN 00213640 (ISSN), DOI 10.1134/S0021364015180162
Примечания : Cited References: 18. - This work was supported by the Russian Foundation for Basic Research, project nos. 13-02-00523 and 14-02-31237
Аннотация: In the framework of the t–J 1–J 2–V model, the integral equation determining the order parameter Δ(p) of the superconducting phase is derived for an ensemble of strongly correlated fermions on a triangular lattice using the diagram technique for the Hubbard operators. Taking into account the interaction between the Hubbard fermions within two coordination spheres, we demonstrate that the exact analytical solution Δ2(p) of this equation for the superconducting phase with the ((dx2−y2+idxy) symmetry can be expressed as a superposition of two chiral basis functions. This gives rise to a new set of nodal points for the complex parameter Δ2(p). Moreover, at some critical value x c of the charge carrier density, we obtain a gapless phase with six Dirac points. The passing of x through x = x c is accompanied by the topological quantum transition corresponding to the change in the topological parameter Q.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V.
Заглавие : Splitting of the spectrum of fermionic excitations in a topological insulator by charge fluctuations
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [19-02-00348]
Место публикации : JETP Letters. - 2021. - Vol. 114, Is. 12. - P.751-756. - ISSN 0021-3640, DOI 10.1134/S0021364021240097. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 22. - This work was supported by the Russian Foundation for Basic Research (project no. 19-02-00348)
Предметные рубрики: HUBBARD FERMIONS
EDGE STATES
PHASE
SURFACE
Аннотация: It is shown that the intersite Coulomb interaction of electrons in a topological insulator leads to the splitting of the initial energy structure and to the induction of two bands of fluctuation states. As a result, the total spectrum of Fermi excitations of the topological insulator has a four-band structure. The dielectric gap is determined by the energy interval between the bottom of the band of fluctuation states of conduction electrons and the top of the valence band of fluctuation states. Since the band of fluctuation states is narrow, quasiparticles with different effective masses appear.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Korovushkin M. M.
Заглавие : Splitting of the lower subband of Hubbard fermions in the Shubin-Vonsowsky model under the influence of strong intersite correlations
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 112, Is. 1. - P108-120. - ISSN 1063-7761, DOI 10.1134/S1063776110061056
Примечания : Cited References: 26. - We express our deep gratitude to R. O. Zaitsev for numerous remarks and discussions. We are grateful to A. A. Golovnya, A. A. Shklyaev, and V. A. Mitskan for specific advice on the numerical calculations of the mass operator. This work was supported by the "Quantum Condensed Matter Physics" Program of the Presidium of the Russian Academy of Sciences, the Russian Foundation for Basic Research (project no. 10-02-00251), the "Scientific and Scientific-Pedagogical Personnel of Innovational Russian for 2009-2013" Federal Goal-Oriented Program, and the Interdisciplinary Integration Project no. 53 of the Siberian Branch of the Russian Academy of Sciences. One of us (M. K.) thanks Lavrentiev's contest of youth projects of the Siberian Branch of the Russian Academy of Sciences.
Предметные рубрики: NARROW ENERGY BANDS
ELECTRON CORRELATIONS
Ключевые слова (''Своб.индексиров.''): cooper channels--cooper instability--density of electronic state--doping levels--electron concentration--energy structures--hubbard--hubbard operators--interaction energies--intersite correlation--mott-hubbard insulator--nonuniform--renormalization--root mean squares--scattering amplitudes--spectral intensity--split-off band--strongly correlated fermions--sub-bands--doping (additives)--superconducting transition temperature
Аннотация: The diagram technique for Hubbard operators is used to investigate the influence of intersite Coulomb interactions on the energy structure and Cooper instability of strongly correlated fermions. Allowance for intersite correlations in doped Mott-Hubbard insulators is shown to lead to a splitting of the lower subband of Hubbard fermions and to the formation of a band of fluctuation states as soon as the intersite interaction energy becomes comparable to or exceeds the mean kinetic energy. The spectral intensity of the splitoff band is proportional to the root-mean-square fluctuation of the occupation numbers and increases with doping level. The predicted effect changes significantly the structure of the density of electronic states. This leads to a renormalization of the pole of the scattering amplitude in the Cooper channel and manifests itself as a nonuniform (in electron concentration) modification of the dependence of the critical superconducting transition temperature.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Korovushkin M. M.
Заглавие : Renormalization of Energy Structure and Oscillation Period in the de Haas-van Alphen Effect at the Strong Intersite Coulomb Interaction
Разночтения заглавия :авие SCOPUS: Renormalization of energy structure and oscillation period in the de Haas-van Alphen effect at the strong intersite Coulomb interaction
Место публикации : J. Phys. Soc. Jpn.: PHYSICAL SOC JAPAN, 2011. - Vol. 80, Is. 1. - Ст.14703. - С. P. - ISSN 0031-9015, DOI 10.1143/JPSJ.80.014703
Примечания : Cited References: 36. - This study was supported by the program "Quantum Physics of Condensed Matter'' of the Presidium of the Russian Academy of Sciences (RAS), the Russian Foundation for Basic Research (project No. 10-02-00251), the Federal goal-oriented program Scientific Brainpower of the Russian Innovations 2009-2013, and the Siberian Division of RAS (Interdisciplinary Integration project No. 53). One of the authors (M. K.) would like to acknowledge the support of the Lavrentiev's Competition of the Siberian Division of RAS. The authors are grateful to the Physical Society of Japan for financial support in publication.
Предметные рубрики: T-C SUPERCONDUCTOR
EXTENDED HUBBARD-MODEL
CUPRATE SUPERCONDUCTORS
ELECTRON CORRELATIONS
QUANTUM OSCILLATIONS
FERMI-SURFACE
OXIDES
TEMPERATURE
STATE
BANDS
Ключевые слова (''Своб.индексиров.''): strongly correlated electron systems--cuprate superconductors--intersite coulomb interaction--t-v model--de haas-van alphen effect--cuprate superconductors--de haas-van alphen effect--intersite coulomb interaction--strongly correlated electron systems--t-v model
Аннотация: The effect of strong intersite Coulomb correlations on the formation of the electron structure of the t-V model has been studied. A qualitatively new result indicating the occurrence of a split-off band of Fermi states has been obtained. The spectral intensity of this band increases with an increase in doping level and is determined by the mean-square fluctuation of occupation numbers. This results in the transformation of the energy structure and the integrated density of states and in a further decrease in state occupation in the quasimomentum space near the Fermi level as compared with Hubbard renormalization. It has been shown that this effect leads to an increase in the area of the quasimomentum space part limited by the Fermi contour and is important for the analysis of the de Haas-van Alphen oscillations in cuprate superconductors.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M.
Заглавие : Modification of the superconducting order parameter Delta(k) by long-range interactions
Разночтения заглавия :авие SCOPUS: Modification of the superconducting order parameter Δ(k) by long-range interactions
Место публикации : JETP Letters. - 2003. - Vol. 77, Is. 7. - P.381-384. - ISSN 0021-3640, DOI 10.1134/1.1581965
Примечания : Cited References: 18
Предметные рубрики: T-J MODEL
BAND HUBBARD-MODEL
SR2CUO2CL2
Аннотация: It is demonstrated that the inclusion of long-range intersite interactions qualitatively modifies the dependence of a superconducting gap on quasimomentum for both s- and d-symmetry types. In particular, the order parameter of a superconducting phase with the symmetry type depends on two amplitudes and has the form Delta(k) = Delta(1)(cosk(x)-cosk(y)) + Delta(2)(cos2k(x)-cos2k(y)). In this case, the theoretical dependence of the critical temperature on the degree of doping agrees with the experimental dependence. (C) 2003 MAIK "Nauka/Interperiodica".
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Microscopic derivation of the Ginzburg-Landau equations for the periodic Anderson model in the coexistence phase of superconductivity and antiferromagnetism
Коллективы : Russian Foundation for Basic Research [13-02-00523]; regional Grant Siberia [15-42-04372]; RF Presidential Grant [SP-1370.2015.5]
Место публикации : J. Low Temp. Phys.: Springer/Plenum Publishers, 2016. - Vol. 185, Is. 5-6. - P.439-445. - ISSN 0022-2291, DOI 10.1007/s10909-015-1410-y. - ISSN 1573-7357(eISSN)
Примечания : Cited References:11. - This work was supported in part by the Russian Foundation for Basic Research, Grant No. 13-02-00523 and regional Grant Siberia No. 15-42-04372. A.O.Z. acknowledges the support of RF Presidential Grant No. SP-1370.2015.5.
Предметные рубрики: HUBBARD-MODEL
Ключевые слова (''Своб.индексиров.''): ginzburg-landau equations--superconductivity--antiferromagnetism--coexistence phase--periodic anderson model
Аннотация: On the basis of the periodic Anderson model, the microscopic Ginzburg-Landau equations for heavy-fermion superconductors in the coexistence phase of superconductivity and antiferromagnetism have been derived. The obtained expressions are valid in the vicinity of quantum critical point of heavy-fermion superconductors when the onset temperatures of antiferromagnetism and superconductivity are sufficiently close to each other. It is shown that the formation of antiferromagnetic ordering causes a decrease of the critical temperature of superconducting transition and order parameter in the phase of coexisting superconductivity and antiferromagnetism.
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