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1
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Solitons in a Compressible Heisenberg Chain

100%
EN
Nonlinear excitations in a Heisenberg chain coupled to the lattice in the presence of an external field are studied within a semi-classical approach.
2
Content available remote

Solitons in a One-Dimensional Degenerate Hubbard Model

100%
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issue 1
117-128
EN
An effective magnon-lattice Hamiltonian for the degenerate Hubbard chain with electron-phonon interaction is derived and a formalism for the description of solitary magnons is presented.
3
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Boson-Induced Orbital Kondo Effect

100%
EN
The single dot in magnetic field and double quantum dot with broken spin-orbital symmetry are discussed in the boson field environment. It is shown that the time dependent potential induces the Kondo effect, provided that the single boson energy compensates the spin or orbital splitting. The photon induced recovery of orbital degeneracy can occur within the same spin channel or with the spin mixing. In the former case the spin polarized photocurrent is expected.
EN
Electron tunneling through a double quantum dot side coupled to a pair of leads is examined in finite-U slave boson mean field approach. Both the two-impurity Kondo regime at half filling and one-and three-electron Kondo effects are analyzed. Special attention is paid to the case when one of the dots is coupled to ferromagnetic lead and another to nonmagnetic. Depending on the gate voltage, the same or opposite sign of polarizations of conductance of the leads is observed.
5
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Two Kondo Impurities in Armchair Graphene Nanoribbon

64%
EN
An interplay of the Kondo effect and inter-impurity correlations in the armchair graphene nanoribbon is studied in the mean field slave boson approach. The effect of the hole doping is examined.
6
64%
EN
The out-of-equilibrium electron transport of carbon nanotube semiconducting quantum dot placed in a magnetic field is studied in the Kondo regime by means of the non-equilibrium Green functions. The equation of motion method is used. For parallel magnetic field the Kondo peak splits into four peaks, following the simultaneous splitting of the orbital and spin states. For perpendicular field orientation the triple peak structure of density of states is observed with the central peak corresponding to orbital Kondo effect and the satellites reflecting the spin and spin-orbital fluctuations.
EN
Thermoelectric effects in a carbon nanotube quantum dot in the Kondo regime are studied by the equation of motion method. The thermopower is highly sensitive to the structure of the spectral density near the Fermi edge. For temperatures close to the Kondo temperature the thermopower approaches a local minimum, which becomes sharper for orbital energies closer to the Fermi level. For higher temperatures the tjermopower increases, but in the temperature range corresponding to charging energy it again drops and achieves significant negative values. We examine the consequences of symmetry breaking of spin-orbital SU(4) system on thermopower.
EN
The spin-resolved current of carbon nanotube quantum dot coupled to ferromagnetic electrodes and influenced by spin-flip scattering is studied in the Kondo regime by the equation of motion method.
EN
The impact of symmetry breaking perturbations on the spin dependent transport through carbon nanotube quantum dots in the Kondo regime is discussed. The proposals of spin filter, spin valve and spin battery are presented.
10
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Tunnel Magnetoresistance in Carbon Nanotube Quantum Dot

64%
EN
The out-of-equilibrium transport properties of carbon nanotube quantum dot in the Kondo regime are studied by means of the non-equilibrium Green function. The equation of motion method is used. The influence of the polarization of electrodes and orbital level splitting, as well as left-right asymmetry, on the spin polarizations of differential conductance are discussed. For zero bias voltage and orbitally degenerate states the SU(4) symmetry of Kondo state is preserved for antiparallel configuration of polarizations of electrodes, whereas it is broken for parallel. In the former case a suppression of linear conductance with increasing polarization is observed. In the latter the behaviour is nonmonotonic due to splitting of the Kondo peak and bringing closer one of the peaks to the Fermi level with increasing polarization. This gives rise to giant tunnel linear magnetoresistance for large polarization.
11
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Dynamic Crystal Field in CePb_{3}

64%
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2000
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vol. 97
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issue 1
245-248
EN
The crystal field of valence fluctuating systems is time dependent due to f-electron transfers to the conduction band. We examine the effects of crystal field fluctuations on the neutron spectra, the specific heat and susceptibility of CePb_{3}.
12
Content available remote

Strained Tetragonal Bain Paths in Fe_{3}Pt Invar

64%
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2000
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vol. 97
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issue 5
749-752
EN
Employing the LMTO-ASA method we calculated the total energy variation of Fe_{3}Pt along the tetragonal distortion path connecting fcc and bcc structures for isotropic biaxial path and uniaxially strained path and compare the results with energies for the unstrained path.
EN
Spin-polarized transport through a quantum dot side attached to a topological superconductor and coupled to a pair of normal leads is discussed in Coulomb and Kondo regimes. For discussion of Coulomb range equation of motion method with extended Hubbard I approximation is used and Kondo regime is analyzed by Kotliar-Ruckenstein slave boson approach. Apart from the occurrence of zero bias anomaly the presence of Majorana states reflects also in splitting of Coulomb lines. In the region of Coulomb borders the spin dependent negative differential conductance is observed. Due to the low energy scale of Kondo effect this probe allows for detection of Majorana states even for extremely weak coupling with topological wire. In this range no signatures of Majorana states appear in Coulomb blockade dominated transport.
EN
We examine transport through a spin-1/2 Kondo impurity, patterned between atomic scale electrodes in the presence of side-coupled nanographene flake. Impurity is attached to the edge of the flake, what allows to test the edge states. The Kotliar Ruckenstein slave boson approach is adopted to describe the strongly correlated impurity. We show that transport measurement of Fano-Kondo effect can serve as a spectroscopic probe of spin resolved graphene flake energy levels. The edge moments can be completely suppressed by gate voltage.
EN
Conductance quantization of heterocontacts between tungsten (W) tip and cubic RCu_5 (R = Gd, Ho, Lu) binary compounds prepared by melt-spinning was observed in nanowires produced dynamically using piezoelectric actuator. The conductance stepwise behaviour of the nanowires was directly observed with a storage oscilloscope. Quantum units of the nanowires conductance measured in their paramagnetic states are presented and discussed in terms of the Landauer formalism.
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