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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Kokorina E. E., Pchelkina Z. V.
Заглавие : Dominance of many-body effects over the one-electron mechanism for band structure doping dependence in Nd2-xCexCuO4: the LDA + GTB approach
Разночтения заглавия :авие SCOPUS: Dominance of many-body effects over the one-electron mechanism for band structure doping dependence in Nd2-xCexCuO4: The LDA+GTB approach
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2007. - Vol. 19, Is. 48. - Ст.486203. - ISSN 0953-8984, DOI 10.1088/0953-8984/19/48/486203
Примечания : Cited References: 36
Предметные рубрики: NARROW ENERGY BANDS
HUBBARD-MODEL
SUPERCONDUCTORS
DENSITY
TEMPERATURE
ORBITALS
WAVE
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--band structure--correlation methods--crystal structure--local density approximation--superconducting materials--electronic correlations--fermionic quasiparticles--neodymium compounds
Аннотация: In the present work we report band structure calculations for the high-temperature superconductor Nd2-xCexCuO4 in the regime of strong electronic correlations within an LDA + GTB method, which combines the local density approximation (LDA) and the generalized tight-binding method (GTB). The two mechanisms of band structure doping dependence were taken into account. Namely, the one-electron mechanism provided by the doping dependence of the crystal structure, and the many-body mechanism provided by the strong renormalization of the fermionic quasiparticles due to the large on-site Coulomb repulsion. We have shown that, in the antiferromagnetic and in the strongly correlated paramagnetic phases of the underdoped cuprates, the main contribution to the doping evolution of the band structure and Fermi surface comes from the many-body mechanism.
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2.

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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3.

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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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : PARLINSKI K., CURRAT R., VETTIER C., ALEKSANDROVA I. P., ECKOLD G.
Заглавие : Effect of hydrostatic-pressure on modulated phases in Rb2ZnBr4
Разночтения заглавия :авие SCOPUS: Effect of hydrostatic pressure on modulated phases in Rb2ZnBr4
Место публикации : Phys. Rev. B. - 1992. - Vol. 46, Is. 1. - P.106-114. - ISSN 0163-1829, DOI 10.1103/PhysRevB.46.106
Примечания : Cited References: 36
Предметные рубрики: INCOMMENSURATE PHASES
NEUTRON-SCATTERING
X-RAY
COMMENSURATE
TRANSITIONS
EVOLUTION
MODEL
WAVE
Аннотация: Neutron-diffraction studies on modulated Rb2ZnBr4, carried out under hydrostatic pressure, revealed two new commensurate phases characterized by wave vectors q = 2/7b* and q = 1/4b*, respectively. The first order phase transition between them is revealed by the coexistence of two distinct peaks in the diffraction pattern. The observed pressure-temperature phase diagram contains: the above-mentioned phases, the ferroelectric commensurate phase q = 1/3, and a region characterized by wave-vector values in the interval q = 2/7-1/3. In this region the modulation wave vector exhibits stepwise behavior as a function of pressure, but remains nearly constant iii temperature runs. We have found in this region a characteristic memory effect in which two temperature runs performed at the same pressure lead to two different modulation wave-vector values, while only the thermal history of the sample is different in the two runs. At ambient pressure we confirm the presence of a multipeaked diffraction pattern just above the lock-in transition to the commensurate q = 1/3 phase. At 122 K the phase transition from the 1/3 phase to the 1/4 phase is detected in pressure scans. The transition mechanism involves the q = 2/7 phase, at least as a metastable intermediate phase.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krasnov I. V.
Заглавие : All-optical confinement of ultracold plasma with resonant ions
Место публикации : Phys. Lett. A: ELSEVIER SCIENCE BV, 2009. - Vol. 373, Is. 26. - P2291-2297. - ISSN 0375-9601, DOI 10.1016/j.physleta.2009.04.042
Примечания : Cited References: 40
Предметные рубрики: RADIATION-PRESSURE
NEUTRAL PLASMAS
POTENTIAL WELLS
ATOMIC MOTION
LIGHT-FIELD
FORCE
SUPERLATTICE
RECTIFICATION
WAVE
Ключевые слова (''Своб.индексиров.''): laser cooling and trapping--ultracold neutral plasma--rectified radiation forces--laser cooling and trapping--rectified radiation forces--ultracold neutral plasma
Аннотация: The solution of the problem of all-optical (nonmagnetic) confinement of ultracold electron-ion neutral plasma based on selective action on plasma ions with quantum transition J = 1 - J = 0 of so-called rectified radiation forces in a strong nonmonochromatic light field is suggested. The presented scheme of the three-dimensional dissipative optical trap for plasma allows one to obtain long-lived ultracold plasma with controlled characteristics. The lifetime of the ultracold plasma in such a trap may exceed considerably (by orders of magnitude) the time of free plasma expansion and the lifetime in the (earlier proposed) optical molasses for the ultracold plasma. (C) 2009 Elsevier B.V. All rights reserved.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M.
Заглавие : Dynamicalmagnetic susceptibility in the spin-fermion model for cuprate superconductors
Коллективы : Russian Foundation for Basic Research [16-02-00073]; Krasnoyarsk Kray Foundation for Scientific and Technical Progress [16-42-240435]; Siberian Branch of the Russian Academy of Sciences [II.2P, 0356-2015-0405]; Administration of Krasnoyarsk Kray
Место публикации : Theor. Math. Phys. - 2017. - Vol. 193, Is. 3. - P.1853-1864. - ISSN 0040-5779, DOI 10.1134/S004057791712011X. - ISSN 1573-9333(eISSN)
Примечания : Cited References:35. - This research was supported by the Russian Foundation for Basic Research (Grant No. 16-02-00073), the Administration of Krasnoyarsk Kray and the Krasnoyarsk Kray Foundation for Scientific and Technical Progress (Grant No. 16-42-240435), and the complex program No. II.2P of the Siberian Branch of the Russian Academy of Sciences (Grant No. 0356-2015-0405).
Предметные рубрики: T-J MODEL
LONG-RANGE-ORDER
POLARON
CUO2
EXCITATIONS
LATTICE
WAVE
Ключевые слова (''Своб.индексиров.''): high-temperature conductor--spin-fermion model--magnetic susceptibility--spin polaron
Аннотация: Using the method of diagram techniques for the spin and Fermi operators in the framework of the SU(2)-invariant spin-fermion model of the electron structure of the CuO2plane of copper oxides, we obtain an exact representation of the Matsubara Green’s function D⊥(k, iω m ) of the subsystem of localized spins. This representation includes the Larkin mass operator ΣL(k, iω m ) and the strength and polarization operators P(k, iω m ) and Π(k, iω m ). The calculation in the one-loop approximation of the mass and strength operators for the Heisenberg spin system in the quantum spin-liquid state allows writing the Green’s function D⊥(k, iω m ) explicitly and establishing a relation to the result of Shimahara and Takada. An essential point in the developed approach is taking the spin-polaron nature of the Fermi quasiparticles in the spin-fermion model into account in finding the contribution of oxygen holes to the spin response in terms of the polarization operator Π(k, iω m ).
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zamkova N. G., Gavrichkov V. A., Sandalov I. S., Ovchinnikov S. G.
Заглавие : Proximity of Ferromagnetic Nickel to Paramagnetic Instability
Коллективы : Russian Foundation for Basic Research [16-02-00273]
Место публикации : JETP Letters. - 2019. - Vol. 109, Is. 4. - P.276-279. - ISSN 0021-3640, DOI 10.1134/S0021364019040131. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 21. - This work was supported by the Russian Foundation for Basic Research (project no. 16-02-00273).
Предметные рубрики: TOTAL-ENERGY CALCULATIONS
WAVE
Аннотация: The phase diagram of Ni in the space of the parameters has been studied within the Kanamori model with the parameters determined from comparison with ab initio calculations for ferromagnetic Ni. The proximity of Ni to the boundary of the transition to a paramagnetic state has been found.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zamkova N. G., Korzhavyi, Pavel, Sandalov I. S.
Заглавие : Inducing magnetism in non-magnetic α-FeSi2 by distortions and/or intercalations
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science [17-42-240212, 18-42-243019]
Место публикации : Phys. Chem. Chem. Phys. - 2019. - Vol. 21, Is. 25. - P.13835-13846. - ISSN 1463-9076, DOI 10.1039/c9cp02361e. - ISSN 1463-9084(eISSN)
Примечания : Cited References: 27. - The reported study was funded by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research projects No 17-42-240212: "Quantum-mechanical simulation of the physical properties of correlated electron materials to improve their functional characteristics" and No 18-42-243019: "First-principles studies of the polarization, magnetic, electronic, and magnetoelectric properties of functional compounds with a spinel structure containing 3d and 4f ions".
Предметные рубрики: TOTAL-ENERGY CALCULATIONS
WAVE
FeSi2
Аннотация: By means of hybrid ab initio + model approach we show that the lattice distortions in non-magnetic α-FeSi2 can induce a magnetic state. However, we find that the distortions required for the appearance of magnetism in non-magnetic α-FeSi2 are too large to be achieved by experimental fabrication of thin films. For this reason we suggest a novel way to introduce magnetism in α-FeSi2 using “chemical pressure” that is, intercalating the α-FeSi2 films by light elements. Theoretical study of the distortions resulting from intercalation reveals that the most efficient intercalants for formation of magnetism and a high spin polarization are lithium, phosphorus and oxygen. Investigation of the dependency of the magnetic moments and spin polarisation on the intercalation atoms concentration shows that the spin polarization remains high even at small concentrations of intercalated atoms, which is extremely important for modern silicate technology.
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