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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Effect of hole doping on the electronic structure and the Fermi surface in the Hubbard model within norm-conserving cluster pertubation theory
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 1. - P.118-131. - ISSN 1063-7761, DOI 10.1134/S1063776111150143
Примечания : Cited References: 51. - This study was supported financially by the Russian Foundation for Basic Research (project nos. 10-02-90725-mob_st and 09-02-00127), Program 18.7 of the Presidium of the Russian Academy of Sciences, the Federal Target Program "Personnel" (state contract no. P891), and the integrated project no. 40 of the Siberian Branch of the Russian Academy of Sciences.
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
NARROW ENERGY-BANDS
CORRELATED ELECTRONS
PSEUDOGAP
EVOLUTION
La2-XSRXCuO4
INSULATOR
Аннотация: The concentration dependences of the band structure, spectral weight, density of states, and Fermi surface in the paramagnetic state are studied in the Hubbard model within cluster pertubation theory with 2 x 2 clusters. Representation of the Hubbard X operators makes it possible to control conservation of the spectral weight in constructing cluster perturbation theory. The calculated value of the ground-state energy is in good agreement with the results obtained using nonperturbative methods such as the quantum Monte Carlo method, exact diagonalization of a 4 x 4 cluster, and the variational Monte Carlo method. It is shown that in the case of hole doping, the states in the band gap (in-gap states) lie near the top of the lower Hubbard band for large values of U and near the bottom of the upper band for small U. The concentration dependence of the Fermi surface strongly depends on hopping to second (t') and third (t '') neighbors. For parameter values typical of HTSC cuprates, the existence of three concentration regions with different Fermi surfaces is demonstrated. It is shown that broadening of the spectral electron density with an energy resolution typical of contemporary ARPES leads to a pattern of arcs with a length depending on the concentration. Only an order-of-magnitude decrease in the linewidth makes it possible to obtain the true Fermi surface from the spectral density. The kinks associated with strong electron correlations are detected in the dispersion relation below the Fermi level.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kolovsky A. R., Buchleitner A.
Заглавие : Quantum chaos in the Bose-Hubbard model
Место публикации : Europhys. Lett. - 2004. - Vol. 68, Is. 5. - P.632-638. - ISSN 0295-5075, DOI 10.1209/epl/i2004-10265-7
Примечания : Cited References: 22
Предметные рубрики: EINSTEIN CONDENSATE
DOUBLE-WELL
TRANSITION
SUPERFLUID
INSULATOR
ATOMS
Аннотация: We present a numerical study of the spectral properties of the 1D Bose-Hubbard model. Unlike the 1D Hubbard model for fermions, this system is found to be non-integrable, and exhibits Wigner-Dyson spectral statistics under suitable conditions.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kolovsky A. R.
Заглавие : New Bloch period for interacting cold atoms in 1D optical lattices
Место публикации : Phys. Rev. Lett.: AMER PHYSICAL SOC, 2003. - Vol. 90, Is. 21. - Ст.213002. - ISSN 0031-9007, DOI 10.1103/PhysRevLett.90.213002
Примечания : Cited References: 19
Предметные рубрики: QUANTUM
TRANSITION
SUPERFLUID
INSULATOR
Аннотация: This paper studies Bloch oscillations of ultracold atoms in an optical lattice, in the presence of atom-atom interactions. A new, interaction-induced Bloch period is identified. Analytical results are corroborated by realistic numerical calculations.
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4.

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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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kudashkin K., Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Spectral properties of the Bose-Hubbard model within the cluster perturbation theory in X-operators representation
Коллективы : RFBR [16-02-00098, 16-42-243048, 16-42-240511, 16-42-240769]; Government of Krasnoyarsk Territory; Russian President Grant [NSh-7559.2016.2]
Место публикации : J. Supercond. Nov. Magn.: Springer, 2017. - Vol. 30, Is. 1. - P.103-107. - ISSN 1557-1939, DOI 10.1007/s10948-016-3781-y. - ISSN 1557-1947(eISSN)
Примечания : Cited References:16. - This work was supported by RFBR grant 16-02-00098, Government of Krasnoyarsk Territory and RFBR according to the research projects 16-42-243048, 16-42-240511, and 16-42-240769, and the Russian President Grant NSh-7559.2016.2.
Предметные рубрики: TRANSITION
SUPERFLUID
INSULATOR
ATOMS
Ключевые слова (''Своб.индексиров.''): bose-hubbard model--ultracold gases--cluster perturbation theory--density of states--spectral properties
Аннотация: We study the two-dimensional ultracold Bose gas in optical lattice. We use cluster perturbation theory based on Hubbard X-operators to calculate the spectral function and phase diagram of Bose-Hubbard model which is minimal model to describe behavior of ultracold gases in optical lattices. We have analyzed spectral properties of spinless bosons in a square lattice taking into account the short-range correlation.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Averyanov D. V., Tokmachev, Andrey M., Parfenov, Oleg E., Karateev, Igor A., Sokolov I. S., Taldenkov, Alexander N., Platunov M. S., Wilhelm, Fabrice, Rogalev, Andrei, Storchak V. G.
Заглавие : Probing proximity effects in the ferromagnetic semiconductor EuO
Коллективы : NRC "Kurchatov Institute"; Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [19-07-00249]; Russian Science FoundationRussian Science Foundation (RSF) [19-19-00009]
Место публикации : Appl. Surf. Sci. - 2019. - Vol. 488. - P.107-114. - ISSN 0169-4332, DOI 10.1016/j.apsusc.2019.05.191. - ISSN 1873-5584(eISSN)
Примечания : Cited References: 57. - This work is partially supported by NRC "Kurchatov Institute" (synthesis), the Russian Foundation for Basic Research [grant 19-07-00249] (magnetization measurements), and the Russian Science Foundation [grant 19-19-00009] (transport measurements). The measurements have been carried out using the equipment of the resource centers of electrophysical, laboratory X-ray, and electron microscopy techniques of NRC "Kurchatov Institute". The authors also gratefully acknowledge the beamtime allocation (MA-3167) by the ESRF.
Предметные рубрики: INTERFACE
FIELD
POLARIZATION
INSULATOR
SILICON
Аннотация: Ferromagnetic insulators are widely employed to induce magnetic phenomena in adjacent layers via proximity effect. This approach could make non-magnetic materials (ranging from silicon to graphene) available for spintronic applications. Eu chalcogenides, EuO in particular, are highly efficient spin generators but suffer from low Curie temperatures. Here, experiments aimed at T-C increase in EuO by its integration with the ferromagnetic metal Gd are reported. The epitaxial bilayers Gd/EuO are synthesized on different substrates and characterized by a combination of diffraction and microscopy techniques. Their magnetic structure - established with magnetization and transport measurements as well as element-selective X-ray magnetic circular dichroism study - comprises coupled magnetic orders of EuO and Gd. EuO is robust against proximity effects - its T-C is still low, increased at most by a few tens of K. Nevertheless, the results encourage further studies of proximity-enhanced ferromagnetism to extend the range of applications of ultrathin layers of EuO in spintronics.
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