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1.
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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2.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Ponomarev A. V., Madronero J., Kolovsky A. R., Buchleitner A.
Заглавие
: Atomic current across an optical lattice
Место публикации
: Phys. Rev. Lett.: AMER PHYSICAL SOC, 2006. - Vol. 96, Is. 5. - Ст.50404. - ISSN 0031-9007,
DOI
10.1103/PhysRevLett.96.050404
Примечания
: Cited References: 18
Ключевые слова
(''Своб.индексиров.''): crystal lattices--electric conductance--
fermions
--switches--atomic current--microscopic dynamics--optical lattices--atomic physics
Аннотация:
We devise a microscopic model for the emergence of a collision-induced, fermionic atomic current across a tilted optical lattice. Tuning the-experimentally controllable-parameters of the microscopic dynamics allows us to switch from Ohmic to negative differential conductance.
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3.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Val'kov V. V., Dzebisashvili D. M.
Заглавие
: Canted phase of an antiferromagnetic Anderson lattice
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). - P692-693. - ISSN 0921-4526,
DOI
10.1016/j.physb.2006.01.223
Примечания
: Cited References: 5
Ключевые слова
(''Своб.индексиров.''): heavy
fermions
--antiferromagnetic canted phase--antiferromagnetic canted phase--heavy
fermions
--antiferromagnetism--band structure--magnetic field effects--magnetic fields--magnetization--spectrum analysis--thermal effects--antiferromagnetic canted phase--energy spectrum--heavy
fermions
--quasiparticle bands--
fermions
Аннотация:
On the basis of extended periodic Anderson model with anti ferromagnetic (AFM) exchange and s-f exchange interactions the energy spectrum of heavy-fermion (HF) AFM metals is calculated. The quasiparticle band structure in collinear AFM phase is described by four splitted bands one of which is very narrow (order of exchange interaction constant) and lies in the vicinity of a localized level. Application of an external magnetic field causes a canting of the sublattice magnetization and due to s-f exchange interaction strongly modifies the HF band picture. Thus eight different quasiparticle bands appear. Their evolution when temperature and magnetic field change is studied. (c) 2006 Elsevier B.V. All rights reserved.
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4.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Korshunov M. M., Ovchinnikov S. G.
Заглавие
: Doping-dependent evolution of low-energy excitations and quantum phase transitions within an effective model for high-T-c copper oxides
Разночтения заглавия
:авие SCOPUS: Doping-dependent evolution of low-energy excitations and quantum phase transitions within an effective model for high-T c copper oxides
Место публикации
: Eur. Phys. J. B: SPRINGER, 2007. - Vol. 57, Is. 3. - P271-278. - ISSN 1434-6028,
DOI
10.1140/epjb/e2007-00179-2
Примечания
: Cited References: 49
Предметные рубрики:
ELECTRON CORRELATIONS
HUBBARD-MODEL
RANGE-ORDER
DIMENSIONS
WAVE
FERMIONS
SYSTEMS
BANDS
METAL
Ключевые слова
(''Своб.индексиров.''): doping dependent evolution--kinematic correlation functions--low energy excitations--quantum phase transitions--doping (additives)--electric excitation--mean field theory--parameter estimation--phase transitions--quantum theory--copper oxides
Аннотация:
In this paper a mean-field theory for the spin-liquid paramagnetic non-superconducting phase of the p- and n-type high-T-c cuprates is developed. This theory applied to the effective t-t'-t ''-J* model with the ab initio calculated parameters and with the three-site correlated hoppings. The static spin-spin and kinematic correlation functions beyond Hubbard-I approximation are calculated self-consistently. The evolution of the Fermi surface and band dispersion is obtained for the wide range of doping concentrations x. For p-type systems the three different types of behavior are found and the transitions between these types are accompanied by the changes in the Fermi surface topology. Thus a quantum phase transitions take place at x = 0.15 and at x = 0.23.Due to the different Fermi surface topology we found for n-type cuprates only one quantum critical concentration, x = 0.2. The calculated doping dependence of the nodal Fermi velocity and the effective mass are in good agreement with the experimental data.
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5.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Val'kov V. V., Golovnya A. A.
Заглавие
: Effect of Spin Fluctuations on the Superconducting Phase of Hubbard
Fermions
in the t-t'-t"-J* Model
Коллективы
:
Разночтения заглавия
:авие SCOPUS: Effect of spin fluctuations on the superconducting phase of Hubbard
fermions
in the t-t′-t″-J*model
Место публикации
: J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 107, Is. 6. - P996-1008. - ISSN 1063-7761,
DOI
10.1134/S1063776108120091
Примечания
: Cited References: 33. - This work was supported by the Program "Quantum Macrophysics" of the Presidium of the Russian Academy of Sciences, Russian Foundation for Basic Research (project no. 06.02.16100), and Integration project no. 3.4 of the Siberian Branch of the Russian Academy of Sciences.
Предметные рубрики:
SPECTRUM
Ключевые слова
(''Своб.индексиров.''): electric conductivity--
fermions
--integral equations--spin dynamics--spin fluctuations--anomalous components--critical temperatures--electron concentrations--hubbard--hubbard operators--joint effects--large systems--nonhomogeneous equations--one-loop approximations--order parameters--renormalization--scattering process--self energies--spin-fluctuation--strongly correlated electrons--superconducting phase--system of integral equations--superconductivity
Аннотация:
The effect of spin-fluctuation scattering processes on the region of the superconducting phase in strongly correlated electrons (Hubbard
fermions
) is investigated by the diagram technique for Hubbard operators. Modified Gor'kov equations in the form of an infinitely large system of integral equations are derived taking into account contributions of anomalous components P(0 sigma),((sigma) over bar0) of strength operator P. It is shown that spin-fluctuation scattering processes in the one-loop approximation for the t-t'-t"-J* model taking into account long-range hoppings and three-center interactions are reflected by normal (P(0 sigma), (0 sigma)) and anomalous (P(0 sigma), ((sigma) over bar0)) components of the strength operator. Three-center interactions result in different renormalizations of the kernels of the integral equations for the superconducting d phase in the expressions for the self-energy and strength operators. In this approximation for the d-type symmetry of the order parameter for the superconducting phase, the system of integral equations is reduced to a system of nonhomogeneous equations for amplitudes. The resultant dependences of critical temperature on the electron concentrations show that joint effect of long-range hoppings, three-center interactions, and spin-fluctuation processes leads to strong renormalization of the superconducting phase region.
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6.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Val'kov V. V., Korovushkin M. M.
Заглавие
: Energy structure of high-temperature superconductors with the intersite Coulomb interaction
Коллективы
: Russian Academy of Sciences; Russian Foundation for Basic Research [07-02-00226]; RAS; Dynasty Foundation
Место публикации
: Eur. Phys. J. B: SPRINGER, 2009. - Vol. 69, Is. 2. - P219-227. - ISSN 1434-6028,
DOI
10.1140/epjb/e2009-00141-4
Примечания
: Cited References: 26. - 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. 07-02-00226); the Siberian Branch of RAS (Interdisciplinary Integration project no. 53). One of authors (M. K.) would like to acknowledge the support of the Dynasty Foundation.
Предметные рубрики:
HIGH-TC SUPERCONDUCTIVITY
SINGLE-BAND
ELECTRON CORRELATIONS
CU OXIDES
J MODEL
DERIVATION
Ключевые слова
(''Своб.индексиров.''): strongly correlated electron systems; heavy
fermions
--narrow-band systems; intermediate-valence solids--cuprate superconductors--strongly correlated electron systems heavy
fermions
--narrow-band systems intermediate-valence solids--cuprate superconductors--emery model--energy structures--fermi state--integrated density--root mean squares--spectral intensity--copper compounds--corundum--coulomb interactions--electrons--
fermions
--high temperature superconductors--oxide superconductors--superconductivity
Аннотация:
The effect of the intersite Coulomb interaction of
fermions
on the ground state and energy structure of high-temperature superconductors is considered within the three-band Emery model using an extended basis of the irreducible operators orthogonal on Mori. The proposed theory allows prediction of bands of the fluctuation states whose spectral intensity grows with an increase in the root-mean-square fluctuations of the occupation numbers. The increase in these fluctuations in high-temperature superconductors upon doping plays a key role in redistribution of the integrated density of the Fermi states.
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7.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Ovchinnikov S. G., Korshunov M. M., Shneyder E. I.
Заглавие
: Lifshits Quantum Phase Transitions and Rearrangement of the Fermi Surface upon a Change in the Hole Concentration in High-Temperature Superconductors
Коллективы
: Presidium of the Russian Academy of Sciences [5.7]; Russian academy of Sciences; Russian Foundation for Basic Research [09-02-00127]
Разночтения заглавия
:авие SCOPUS: Lifshits quantum phase transitions and rearrangement of the fermi surface upon a change in the hole concentration in high-temperature superconductors
Место публикации
: J. Exp. Theor. Phys. - 2009. - Vol. 109, Is. 5. - Pю775-785. - ISSN 1063-7761,
DOI
10.1134/S1063776109110077
Примечания
: Cited References: 71. - The authors thank A. A. Kordyuk for discussion of the results and T. M. Ovchinnikova for technical assistance in data processing.This study was supported by the program "Quantum Physics of Condensed Media" of the Presidium of the Russian Academy of Sciences (project no. 5.7), integrated project no. 40 of the Siberian Branch-Ural Division of the Russian academy of Sciences, and the Russian Foundation for Basic Research (project no. 09-02-00127).
Предметные рубрики:
T-J MODEL
CORRELATED ELECTRONS
COPPER OXIDES
SPECTRUM
PSEUDOGAP
METAL
FLUCTUATIONS
EXCITATIONS
INSULATOR
SYSTEMS
Ключевые слова
(''Своб.индексиров.''): critical points--cuprates--electron heat--electron structures--experimental data--high-t--layered cuprates--low temperatures--normal phase--quantum oscillations--quantum phase transitions--sign reversal--strong correlation--copper compounds--electronic structure--equations of state--fermi surface--
fermions
--high temperature superconductors--hole concentration--superconductivity--surface structure--phase transitions
Аннотация:
Changes in the electronic structure in the normal phase of high-T-c superconductors (HTSCs), viz., layered cuprates, are considered. The results of LDA + GTB calculations of the electron structure and the Fermi surface of La2-xSrxCuO4 one-layer cuprates with allowance for strong correlations are compared with ARPES and quantum oscillations data. Two critical points x(c1) and x(c2) are discovered at which the rearrangement of the Fermi surface takes place. In the vicinity of these points, changes in the thermodynamic properties at low temperatures are determined using the Lifshits ideology concerning 2.5-order quantum phase transitions. A singularity delta(C/T) proportional to (x-x(e))(1/2) in the electron heat capacity agrees well with the available experimental data in the vicinity of x(c1)approximate to 0.15. Sign reversal of the Hall constant upon doping is also considered qualitatively.
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8.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Korshunov M. M., Eremin I., Efremov D. V., Maslov D. L., Chubukov A. V.
Заглавие
: Nonanalytic Spin Susceptibility of a Fermi Liquid: The Case of Fe-Based Pnictides
Коллективы
: RFBR [09-02-00127]; OFN RAS; APCTP; NSF-DMR [0645461, 0604406]; RMHE [2.1.1/3199]; Laboratoire de Physique des Solides, Universite Paris-Sud (France); RTRA Triangle de la Physique
Разночтения заглавия
:авие SCOPUS: Nonanalytic spin susceptibility of a fermi liquid: The case of Fe-based pnictides
Место публикации
: Phys. Rev. Lett.: AMER PHYSICAL SOC, 2009. - Vol. 102, Is. 23. - Ст.236403. - ISSN 0031-9007,
DOI
10.1103/PhysRevLett.102.236403
Примечания
: Cited References: 41. - We thank R. Klingeler for useful discussions. M. M. K. acknowledges support from RFBR ( 09-02-00127) and the OFN RAS program on "Strong electronic correlations". I. E. acknowledges partial support from APCTP, NSF-DMR ( 0645461), and the RMHE Program ( Contract No. 2.1.1/3199). D. L. M. acknowledges support from Laboratoire de Physique des Solides, Universite Paris-Sud ( France) and RTRA Triangle de la Physique. A. V. C. acknowledges support from NSF-DMR 0604406.
Предметные рубрики:
PHASE-TRANSITIONS
QUANTUM
Ключевые слова
(''Своб.индексиров.''): electron pockets--fermi energy--linear temperature dependence--pnictides--prefactor--quantitative agreement--spin susceptibility--temperature dependence--fermi liquids--
fermions
--liquids--magnetic susceptibility--temperature distribution--spin dynamics
Аннотация:
We propose an explanation of the peculiar linear temperature dependence of the uniform spin susceptibility chi(T) in ferropnictides. We argue that the linear in T term appears to be due to the nonanalytic temperature dependence of chi(T) in a two-dimensional Fermi liquid. We show that the prefactor of the T term is expressed via the square of the spin-density-wave (SDW) amplitude connecting nested hole and electron pockets. Because of an incipient SDW instability, this amplitude is large, which, along with a small value of the Fermi energy, makes the T dependence of chi(T) strong. We demonstrate that this mechanism is in quantitative agreement with the experiment.
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9.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Val'kov V. V., Dzebisashvili D. M.
Заглавие
: Electron spectrum and heat capacity of heavy
fermions
in the canted phase of antiferromagnetic intermetallides
Коллективы
:
Место публикации
: J. Exp. Theor. Phys. - 2010. - Vol. 110, Is. 2. - P.301-318. - ISSN 1063-7761,
DOI
10.1134/S1063776110020147
Примечания
: Cited References: 41. - This study was supported by the program "Quantum Physics of Condensed Media" of the Presidium of the Russian Academy of Sciences, interdisciplinary integration project no. 53 of the Siberian Branch of the Russian Academy of Sciences, and the Russian Foundation for Basic Research (project no. 07-02-00226).
Предметные рубрики:
PERIODIC ANDERSON MODEL
PRESSURE-INDUCED SUPERCONDUCTIVITY
KONDO-LATTICE
FERROMAGNETISM
FLUCTUATIONS
COEXISTENCE
CERHIN5
SYSTEMS
DIAGRAM
CENISN
Ключевые слова
(''Своб.индексиров.''): antiferromagnetic phase--antiferromagnetics--antiferromagnets--electron spectrum--electronic heat capacity--energy spectra--experimental data--external magnetic field--heat capacities--heavy fermion--low temperatures--magnetic sublattices--magnetic subsystems--sommerfeld constant--structural rearrangement--temperature dependence--antiferromagnetism--cerium--cerium compounds--
fermions
--magnetic fields--phase transitions--specific heat--spectroscopy--antiferromagnetic materials
Аннотация:
The energy spectrum of heavy
fermions
in an external magnetic field is calculated for canted magnetic sublattices of antiferromagnetic intermetallides. This makes it possible to determine low-temperature features of electronic heat capacity of heavy-fermion antiferromagnets with the metal-type ground state taking into account the structural rearrangement of the magnetic subsystem. The calculated temperature dependences of the magnetization, heat capacity, and Sommerfeld constant in the vicinity of the point of transition to the antiferromagnetic phase correlate with experimental data obtained for heavy-fermion antiferromagnets PuGa3, Ce2Au2Cd, YbNiSi3, and PuPd5Al2.
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10.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Korshunov M. M., Zakharova E. V., Nekrasov I. A., Pchelkina Z. V., Ovchinnikov S. G.
Заглавие
: The Fermi surface and the role of electronic correlations in Sm2-xCexCuO4
Коллективы
:
Разночтения заглавия
:авие SCOPUS: The Fermi surface and the role of electronic correlations in Sm 2-xCexCuO4
Место публикации
: J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2010. - Vol. 22, Is. 1. - Ст.15701. - ISSN 0953-8984,
DOI
10.1088/0953-8984/22/1/015701
Примечания
: Cited References: 35. - We would like to thank A A Kordyuk and I Eremin for useful discussions. The authors acknowledge support from RFBR (grants 08-02-00021, 10-02-00662, 08-02-91200 and 07-02-00226), the RAS programs on 'Low temperature quantum phenomena', 'Quantum physics of condensed matter' and 'Strongly correlated electrons solids', President of Russia (grants MK-614.2009.2 (IN) and MK-3227.2008.2 (ZP)), Scientific School (grant SS-1929.2008.2), Interdisciplinary UB-SB RAS project, Dynasty Foundation (ZP) and Russian Science Support Foundation (IN).
Предметные рубрики:
T-C SUPERCONDUCTOR
IN-GAP STATES
SPIN CORRELATIONS
BAND
LA2-XSRXCUO4
EXCITATIONS
TRANSITION
EVOLUTION
SM2CUO4
OXIDES
Ключевые слова
(''Своб.индексиров.''): antiferromagnetics--doping evolution--electron-doped--electronic correlation--emery model--experimental data--generalized tight bindings--high-t--hybrid scheme--magnetic orders--spin-liquid--tight binding model--two-regime--antiferromagnetism--cerium--cerium compounds--copper oxides--corundum--doping (additives)--fermi surface--
fermions
--tin--surfaces
Аннотация:
Using a LDA + GTB (local density approximation + generalized tight-binding) hybrid scheme we investigate the band structure of the electron-doped high-T-c material Sm2-xCexCuO4. Parameters of the minimal tight-binding model for this system (the so-called three-band Emery model) were obtained within the NMTO (Nth-order muffin-tin orbital) method. The doping evolution of the dispersion and the Fermi surface in the presence of electronic correlations was investigated in two regimes of magnetic order: short-range (spin-liquid) and long-range (antiferromagnetic metal). Each regime is characterized by the specific topologies of the Fermi surfaces and we discuss their relation to recent experimental data.
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11.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Val'kov V. V., Golovnya A.A., Korovushkin M.M.
Заглавие
: Kinematic mechanism of the modulation of the spectral intensity in the spatially uniform system of Hubbard
fermions
Место публикации
: Journal of Experimental and Theoretical Physics Letters (JETP Letters). - Москва: Pleiades Publishing, Ltd. (Плеадес Паблишинг, Лтд), 2011. - Т. 94, № 3. - С. 197-201. - ISSN 0021-3640,
DOI
10.1134/S0021364011150148. - ISSN 1090-6487(eissn)
РИНЦ
Найти похожие
12.
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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13.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Val'kov V. V., Golovnya A. A., Korovushkin M. M.
Заглавие
: Kinematic mechanism of the modulation of the spectral intensity in the spatially uniform system of Hubbard
fermions
Место публикации
: JETP Letters. - 2011. - Vol. 94, Is. 3. - P.197-201. - ISSN 0021-3640,
DOI
10.1134/S0021364011150148
Примечания
: Cited References: 21. - We are grateful to R.O. Zaitsev and N.M. Plakida for the constructive criticism and helpful discussions. This work was supported by the Presidium of the Russian Academy of Sciences (program "Quantum Physics of Condensed Matter"), the Russian Foundation for Basic Research (project no. 09-02-00127), the Ministry of Education and Science of the Russian Federation (federal program "Scientific and Pedagogical Personnel of Innovative Russia" for 2009-2013), and the Siberian Branch, the Russian Academy of Sciences (integration project no. 53). The work of A.A.G. and M.M.K. was also supported by the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools (grant no. MK-1300-2011.2) and by the Siberian Branch, Russian Academy of Sciences (Lavrent'ev Competition).
Предметные рубрики:
SPIN SUSCEPTIBILITY
ANTIFERROMAGNETS
DYNAMICS
CHARGE
MODEL
Аннотация:
Using the exact representation of the Green's function constructed in terms of the Hubbard operators, it has been shown that the kinematic interaction that induces the spin-fluctuation processes in the spatially uniform system of Hubbard
fermions
leads to significant variations in the spectral intensity A(k, omega) in the Brillouin zone. As a result, the modulation of A(k, omega) appears in the Fermi contour. The sign of the hopping integral within the first coordination sphere is determined by the contour section, where A(k, omega) decreases according to the angle-resolved photoemission spectroscopy data.
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14.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Val'kov V. V., Korovushkin M. M.
Заглавие
: Lower subband splitting and superconductivity of 2D Hubbard
fermions
with strong intersite correlations
Коллективы
: International Symposium "Nanophysics and Nanoelectronics-2011" (March 2011; Nizhni Novgorod)
Место публикации
: Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2012. - Vol. 76, Is. 2. - P.133-135. - ISSN 1062-8738,
DOI
10.3103/S1062873812020074
Примечания
: Cited References: 6. - This study was supported by Quantum Physics of Condensed Matter program of the Presidium of the Russian Academy of Sciences; the Russian Foundation for Basic Research, project np. 10-02-00251; the federal target program Scientists and Science Teachers of an Innovate Russia, 2009-2013; the Siberian Branch of the Russian Academy of Sciences, complex integration project no. 53; RF Presidential Grant MK-1300.2011.2; and the Siberian Branch of the Russian Academy of Sciences' Lavrent'ev Competition for Young Scientists.
Ключевые слова
(''Своб.индексиров.''): coulomb correlations--doping levels--electron structures--fermi state--hubbard--intersite correlation--mean-square fluctuations--spectral intensity--split-off band--subbands--natural sciences
Аннотация:
The effect of the strong intersite Coulomb correlations on the formation of an electron structure in the Shubin-Vonsowsky model in the regime of strong one-site correlations is studied. The results reveal a split-off band of the Fermi states. The spectral intensity of this band grows with the enhancement of the doping level and is determined by the mean-square fluctuation of occupation numbers. This changes the structure of the electron density of states qualitatively. © 2012 Allerton Press, Inc.
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15.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Val'kov V. V., Zlotnikov A. O.
Заглавие
: Effect of pressure on antiferromagnetic and superconducting ordering in systems with heavy
fermions
Коллективы
: International Interdisciplinary Symposium “Ordering in Minerals and Alloys” (14th; 8 -13 Sept. 2011; Rostov-on-Don)
Место публикации
: Bull. Russ. Acad. Sci.: Phys.: Allerton Press, 2012. - Vol. 76, Is. 7. - P.733-736. - ISSN 0022-2860,
DOI
10.3103/S1062873812070362
Примечания
: Cited References: 7. - This work was supported by the Department of Physical Sciences, Russian Academy of Sciences (the Strong Electron Correlations Program); the Russian Foundation for Basic Research, projects nos. 100200251 and 110200741; the RFBR Sibir’, project no. 110298007; and by the federal target program Scientific and Pedagogical Personnel of an Innovative Russia, 2009–2013.
Ключевые слова
(''Своб.индексиров.''): antiferromagnetic orderings--antiferromagnetic orders--antiferromagnetic phasis--antiferromagnetics--cooper instability--effect of pressure--external pressures--heavy fermion--impurity level--localized state--periodic anderson model--seed energy--spin moments--superconducting ordering--superexchange interaction--superconductivity--antiferromagnetism
Аннотация:
Characteristics of the superconducting and antiferromagnetic phases of heavy-fermion intermet-allides are described within a periodic Anderson model with allowance for the superexchange interaction between spin moments of the localized states. It is shown that an external pressure that changes the seed energy of an impurity level can rapidly destroy the long-range antiferromagnetic order. The development of the Cooper instability near such an order-disorder transition induces the experimentally observed state in which superconductivity coexists with the antiferromagnetic ordering. В© 2012 Allerton Press, Inc.
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16.
Вид документа
: Статья из сборника (однотомник)
Шифр издания
:
Автор(ы)
: Ovchinnikov S. G., Korshunov M. M., Nikolaev S. N., Shneyder E. I.
Заглавие
: Quantum phase transitions and superconductivity in single- and two-layer cuprates in the multiband theory of Hubbard
fermions
Коллективы
: Ettore Majorana Foundation, Centre for Scientific Culture, Rome International Center for Materials Science, International School of Solid State Physics, "Phase separation and Superstripes in High Temperature Superconductors and Related Materials", Int. Conf. (55; 2012 ; July ; 11-17; Erice (Sicily), Italy)
Место публикации
: International conferences «Phase separation and Superstripes in High Temperature Superconductors and Related Materials (Superstripes-2012)». - 2012. - P.128
Аннотация:
We consider the doping dependence of the normal and superconducting properties of LaSrCuO and YBaCuO in the low energy effective model based on the ab initio LDA+GTB calculations. With doping we have found a concentration region with electronic instability of the uniform state. We have shown that two quantum phase transitions (QPT) of the Lifshitz type correspond well to the experimental phase diagram. For superconducting state we have considered both magnetic and phonon mechanisms of pairing.
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17.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Ovchinnikov S. G., Korshunov M. M., Makarov I. A., Shneyder E. I.
Заглавие
: Quantum phase transitions and superconductivity in single- and two-layer cuprates in the multiband theory of Hubbard
fermions
Место публикации
: J. Supercond. Nov. Magn. - 2013. - Vol. 26, Is. 8. - P.2607-2609. - ISSN 1557-1939,
DOI
10.1007/s10948-013-2144-1. - ISSN 1557-1947
Аннотация:
We consider the doping dependence of the normal and superconducting properties of La2Sr2−x CuO2 and YBa2Cu3O7 in the low energy effective model based on the ab initio LDA+GTB calculations. With doping we have found a concentration region with electronic instability of the uniform state. We have shown that two quantum phase transitions (QPT) of the Lifshitz type correspond well to the experimental phase diagram. For superconducting state we have considered both magnetic and phonon mechanisms of pairing.
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18.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Shneyder E. I., Spitaler J., Kokorina E. E., Nekrasov I. A., Gavrichkov V. A., Draxl C., Ovchinnikov S. G.
Заглавие
: Coupling of Hubbard
fermions
with phonons in La2 CuO4: A combined study using density-functional theory and the generalized tight-binding method
Место публикации
: J. Alloys Compd.: Elsevier, 2015. - Vol. 648. - P.258-264. - ISSN 0925-8388,
DOI
10.1016/j.jallcom.2015.05.150
Примечания
: Cited References: 60. - We acknowledge the stimulating discussions with V.V. Val'kov, D.M. Dzebisashvilly, M.M. Korshunov and I.S. Sandalov. E.I.S. and S.G.O. are thankful to the Russian Science Foundation (project No. 14-12-00061) for the support of the research given in Sections 2, 6 and 7. E.E.K. and I.A.N. are thankful to the State Contract No. 0389-2014-0001 and RFBR grant No. 14-02-00065 for the support of the research given in Section 5. Financial support of the research given in Sections 3 and 4 by the Austrian Federal Government (in particular from Bundesministerium fur Verkehr, Innovation und Technologie and Bundesministerium fur Wissenschaft, Forschung und Wirtschaft) represented by Osterreichische Forschungsforderungsgesellschaft mbH and the Styrian and the Tyrolean Provincial Government, represented by Steirische Wirtschaftsforderungsgesellschaft mbH and Standortagentur Tirol, within the framework of the COMET Funding Programme is gratefully acknowledged by C.D. and J.S.
Предметные рубрики:
MEAN-FIELD THEORY
LINEAR-RESPONSE THEORY
CUPRATE SUPERCONDUCTORS
ELECTRONIC-STRUCTURE
CORRELATED SYSTEMS
LATTICE-DYNAMICS
BAND-STRUCTURE
LA2CUO4
MODEL
LA2-XSRXCUO4
Ключевые слова
(''Своб.индексиров.''): high-temperature superconductivity--electron-phonon coupling--density-functional theory--generalized tight-binding approach
Аннотация:
We present results for the electron-phonon interaction of the Γ-point phonons in the tetragonal high-temperature phase of La2 CuO4 obtained from a hybrid scheme, combining density-functional theory (DFT) with the generalized tight-binding approach. As a starting point, eigenfrequencies and eigenvectors for the Γ-point phonons are determined from DFT within the frozen phonon approach utilizing the augmented plane wave + local orbitals method. The so obtained characteristics of electron-phonon coupling are converted into parameters of the generalized tight-binding method. This approach is a version of cluster perturbation theory and takes the strong on-site electron correlations into account. The obtained parameters describe the interaction of phonons with Hubbard
fermions
which form quasiparticle bands in strongly correlated electron systems. As a result, it is found that the Γ-point phonons with the strongest electron-phonon interaction are the A2u modes (236 cm-1, 131 cm-1 and 476 cm-1). Finally it is shown, that the single-electron spectral-weight redistribution between different Hubbard fermion quasiparticles results in a suppression of electron-phonon interaction which is strongest for the triplet Hubbard band with z oriented copper and oxygen electrons. © 2015 Elsevier B.V. All rights reserved.
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19.
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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20.
Вид документа
: Статья из журнала
Шифр издания
:
Автор(ы)
: Fedorov A. S., Popov Z. I., Kuzubov A. A., Visotin M. A.
Заглавие
: Prediction and theoretical investigation of new 2D and 3D periodical structures, having graphene-like bandstructures
Место публикации
: Phys. Status Solidi B. - 2015. - Vol. 252, Is. 11. - P.2407-2411. - ISSN 0370-1972,
DOI
10.1002/pssb.201552226
Примечания
: Cited References: 27. - This work was supported by the Ministry of Education and Science of Russia (Russian-Japanese joined project, Agreement No. 14.613.21.0010, ID RFMEFI61314 x 0010). The authors are grateful to the Joint Supercomputer Center of Russian Academy of Sciences, Moscow and Siberian Supercomputer Center (SSCC) of SB RAS, Novosibirsk for the opportunity of using their computer clusters to perform the calculations
Предметные рубрики:
BRILLOUIN-ZONE INTEGRATIONS
INITIO MOLECULAR-DYNAMICS
AUGMENTED-WAVE METHOD
DIRAC
FERMIONS
ELECTRON-GAS
TRANSITION
POINTS
Ключевые слова
(''Своб.индексиров.''): dft calculations--dirac cones--graphene--nanoparticles
Аннотация:
A new family of planar nanostructures having graphene-like electronic band structure is theoretically investigated by density functional theory (DFT). Based on general perturbation theory and a tight-binding model, it was shown that graphene-like planar structures, consisting of identical nanoparticles with relatively weak contacts between them, should have an electronic band structure with Dirac cones. Two such structures, consisting of 71- or 114-silicon atom nanoparticles, were investigated by DFT using VASP software package. The band-structure calculations show the presence of Dirac cones with electron group velocity equal to 1.05 × 105 and 0.53 × 105 m/s, respectively. By generalizing the theory, a new family of 3D structures having intersecting areas with linear dispersion in the band structures was derived. As an example, the band structure of identical 25-atom silicon nanoclusters arranged in a simple cubic lattice was calculated. It was shown that the band structure has features similar to the Dirac cones.
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