| 2091. |
- Zhou, Yan, et al.
(författare)
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Oscillatory transient regime in the forced dynamics of a nonlinear auto oscillator
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:1, s. 012408-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that the forced transient dynamics of a nonlinear (nonisochronous) auto-oscillator is qualitatively different from the dynamics of a quasilinear oscillator described by the classical Adler's model. If the normalized amplitude mu of the driving force exceeds a certain critical value mu(cr), the transition to the synchronized regime becomes oscillatory with a frequency proportional to proportional to root mu-mu(cr) and a synchronization time that is almost independent of mu. The discovered effect is illustrated on the example of a strongly nonlinear spin torque nano-oscillator (STNO) where the finite transient synchronization time can limit the possible range of STNO modulation frequencies.
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| 2092. |
- Zivkovic, Marko, et al.
(författare)
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Sagnac rotational phase shifts in a mesoscopic electron interferometer with spin-orbit interactions
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 77:11
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Tidskriftsartikel (refereegranskat)abstract
- The Sagnac effect is an important phase coherent effect in optical and atom interferometers where rotations of the interferometer with respect to an inertial reference frame result in a shift in the interference pattern proportional to the rotation rate. Here, we analyze the Sagnac effect in a mesoscopic semiconductor electron interferometer. We include in our analysis the Rashba spin-orbit interactions in the ring. Our results indicate that spin-orbit interactions increase the rotation-induced phase shift. We discuss the potential experimental observability of the Sagnac phase shift in such mesoscopic systems.
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| 2093. |
- Zolyomi, V., et al.
(författare)
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Anomalous surface relaxation in hcp transition metals
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:19
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Tidskriftsartikel (refereegranskat)abstract
- First-principles total-energy calculations indicate anomalously large surface relaxations for groups IVA and VIIA hcp metals. In addition, for group VIIA elements the magnitude of the layer relaxation exhibits an unusually slow decay with the distance from the surface. We argue that the above phenomena can be traced back to the peculiar Fermi surface of groups IVA and VIIA hcp metals. Namely, the anomalous surface relaxation appears as a consequence of low-energy excitations with near 2k(F) wave vectors, which is also reflected by the flat and degenerate d bands located close to the Fermi level in the L-A-H plane of the hcp Brillouin zone.
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| 2094. |
- Zozoulenko, Igor, 1962-, et al.
(författare)
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Hysteresis and spin phase transitions in quantum wires in the integer quantum Hall regime
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - College Park, MD, USA : American Physical Society. - 1098-0121 .- 1550-235X. ; 75:3, s. 035318-1-035318-5
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that a split-gate quantum wire in the integer quantum Hall regime can exhibit electronic transport hysteresis for up- and down-sweeps of a magnetic field. This behavior is shown to be due to phase spin transitions between two different ground states with and without spatial spin polarization in the vicinity of the wire boundary. The observed effect has a many-body origin arising from an interplay between a confining potential, Coulomb interactions, and the exchange interaction. We also demonstrate and explain why the hysteretic behavior is absent for steep and smooth confining potentials and is present only for a limited range of intermediate confinement slopes. © 2007 The American Physical Society.
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| 2095. |
- Zozoulenko, Igor, 1962-, et al.
(författare)
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Quenching of compressible edge states around antidots
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:20, s. 201303-
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Tidskriftsartikel (refereegranskat)abstract
- We provide a systematic quantitative description of the edge state structure around a quantum antidot in the integer quantum Hall regime. The calculations for spinless electrons within the Hartree approximation reveal that the widely used Chklovskii electrostatic description [Phys. Rev. B 46, 4026 (1992)] greatly overestimates the widths of the compressible strips, the difference between these approaches diminishes as the size of the antidot increases. By including spin effects within density functional theory in the local spin-density approximation, we demonstrate that the exchange interaction can suppress the formation of compressible strips and lead to a spatial separation between the spin-up and spin-down states. As the magnetic field increases, the outermost compressible strip related to spin-down states starts to form. However, in striking contrast to quantum wires, the innermost compressible strip (due to spin-up states) never develops for antidots. © 2006 The American Physical Society.
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| 2096. |
- Zozoulenko, Igor, 1962-, et al.
(författare)
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Spatial spin polarization and suppression of compressible edge channels in the integer quantum Hall regime
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 73:15, s. 155314-
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Tidskriftsartikel (refereegranskat)abstract
- We perform systematical numerical studies of the structure of spin-resolved compressible strips in split-gate quantum wires taking into account the exchange and correlation interaction within the density functional theory in the local spin-density approximation. We find that for realistic parameters of the wire the exchange interaction can completely suppress the formation of the compressible strips. As the depletion length or magnetic field are increased, the compressible strips starts to form first for the spin-down and then for spin-up edge channels. We demonstrate that the widths of these strips plus the spatial separation between them caused by the exchange interaction is equal to the width of the compressible strip calculated in the Hartree approximation for spinless electrons. We also discuss the effect of electron density on the suppression of the compressible strips in quantum wires. © 2006 The American Physical Society.
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| 2097. |
- Zozoulenko, Igor, 1962-, et al.
(författare)
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Spin polarization of edge states and the magnetosubband structure in quantum wires
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 73:7, s. 075331-
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Tidskriftsartikel (refereegranskat)abstract
- We provide a quantitative description of the structure of edge states in split-gate quantum wires in the integer quantum Hall regime. We develop an effective numerical approach based on the Green's function technique for the self-consistent solution of Schrödinger equation where electron and spin interactions are included within the density functional theory in the local spin density approximation. We use the developed method to calculate the subband structure and propagating states in the quantum wires in perpendicular magnetic field starting with a geometrical layout of the wire. We discuss how the spin-resolved subband structure, the current densities, the confining potentials, as well as the spin polarization of the electron and current densities evolve when an applied magnetic field varies. We demonstrate that the exchange and correlation interactions dramatically affect the magnetosubbands in quantum wires bringing qualitatively new features in comparison to a widely used model of spinless electrons in Hartree approximation. © 2006 The American Physical Society.
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| 2098. |
- Zozoulenko, Igor, et al.
(författare)
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Time-resolved dynamics of electron wave packets in chaotic and regular quantum billiards with leads
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:8
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Tidskriftsartikel (refereegranskat)abstract
- We perform numerical studies of wave packet propagation through open quantum billiards whose classical counterparts exhibit regular and chaotic dynamics. We show that for tless than or similar totau(H)(tau(H) being the Heisenberg time), the features in the transmitted and reflected currents are directly related to specific classical trajectories connecting the billiard leads. When tgreater than or similar totau(H), the calculated quantum-mechanical current starts to deviate from its classical counterpart, with the decay rate obeying a power law that depends on the number of decay channels. In a striking contrast to the classical escape from chaotic and regular systems (exponentially fast e(-gammat) for the former versus power-law t(-xi) for the latter), the asymptotic decay of the corresponding quantum systems does not show a qualitative difference.
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| 2099. |
- Zubkov, V. G., et al.
(författare)
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Structural, vibrational, electronic, and luminescence properties of the cyclotetravanadates A(2)M(VO3)(4) (A=Na,Ag; M=Ca,Sr)
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 77, s. 174113-
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Tidskriftsartikel (refereegranskat)abstract
- The physical properties of the family of cyclotetravanadates A(2)M(VO3)(4), where A=Na,Ag and M=Ca,Sr, have been studied by means of x-ray powder diffraction, neutron diffraction, electron diffraction, infrared, Raman, NMR, photoexcitation and pulse cathode beam excitation, and x-ray photoelectron spectroscopies, and band structure calculations. The differences between the structural, vibrational, luminescence, and electronic properties of the alkali metal-containing [Na2Ca(VO3)(4) and Na2Sr(VO3)(4)] and the d metal-containing cyclotetravanadates [Ag2Ca(VO3)(4) and Ag2Sr(VO3)(4)] are analyzed. Na2Ca(VO3)(4), Ag2Ca(VO3)(4), Na2Sr(VO3)(4), and Ag2Sr(VO3)(4) have tetragonal structures, P4/nbm, with a=10.438 49(6), 10.445 24(5), 10.634 49(4), and 10.625 74(6), and c=4.938 73(5), 4.968 45(5), 4.962 05(4), and 4.979 30(4) angstrom, respectively. The main structural feature of A(2)M(VO3)(4) is the tetracyclic [V4O12] units. The hybridized O 2p-V 3d states of the tetracyclic [V4O12] units have a dominant influence on the electronic structure of these compounds. The compounds are semiconducting with a local density approximation band gap increasing, from 1.85 eV for Ag2Ca(VO3)(4) to 3.02 eV for Na2Ca(VO3)(4). The prospects of these compounds as advanced materials for detectors of photon and corpuscular radiation as well as for color correction of light emission sources such as lamp and light emitting diode sources are discussed.
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| 2100. |
- Zvyagin, A. A., et al.
(författare)
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Spin-orbit and impurity scattering in an integrable electron model: Exact results for dynamic correlations
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 89
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Tidskriftsartikel (refereegranskat)abstract
- We introduce an integrable model of spin-polarized interacting electrons subject to a spin-conserving spin-orbit interaction. Using the Bethe ansatz and conformal field theory, we calculate the exact large-time single-electron and density correlations and find that while the spin-orbit interaction enhances the single-electron Green's function, the density correlations get suppressed. Adding a localized impurity and coupling it to the electrons so that integrability is preserved, the dynamic correlations are found to change significantly after a quantum quench with the impurity interaction switched on suddenly. When the electrons are confined to a periodic structure, the correlations are indifferent to the location of the impurity and only carry an imprint of its intrinsic properties. We conjecture that this unusual feature originates from the integrability of the model.
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