| 11. |
- Dolbin, Alexander V, et al.
(författare)
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The effect of O2 impurities on the low-temperature radial thermal expansion of bundles of closed single-walled carbon nanotubes
- 2011
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : American Institute of Physics (AIP). - 1063-777X .- 1090-6517. ; 37:4, s. 343-346
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Tidskriftsartikel (refereegranskat)abstract
- The effect of oxygen impurities upon the radial thermal expansion αr of bundles of closed single-walled carbon nanotubes has been investigated in the temperature interval 2.2–48 K by the dilatometric method. Saturation of bundles of nanotubes with oxygen caused an increase in the positive αr-values in the whole interval of temperatures used. Also, several peaks appeared in the temperature dependence αr(T) above 20 K. The low temperature desorption of oxygen from powders consisting of bundles of single-walled nanotubes with open and closed ends has been investigated.
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| 12. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
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Dynamics of current-induced magnetic superstructures in exchange-spring devices
- 2012
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 38:7, s. 626-632
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Tidskriftsartikel (refereegranskat)abstract
- Thermoelectric manipulation of the magnetization of a magnetic layered stack in which a low-Curie temperature magnet is sandwiched between two strong magnets (exchange spring device) is considered. Controllable Joule heating produced by a current flowing in the plane of the magnetic stack (CIP configuration) induces a spatial magnetic and thermal structure along the current flow - a magnetothermal-electric domain (soliton). We show that such a structure can experience oscillatory in time dynamics if the magnetic stack is incorporated into an electric circuit in series with an inductor. The excitation of these magnetothermionic oscillations follow the scenario either of “soft” or “hard” instability: in the latter case oscillations arise if the initial perturbation is large enough. The frequency of the temporal oscillations is of the order of 105–107s–1 for current densities j∼106–107A/cm2.
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| 13. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
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Microwave-induced spin-flip scattering of electrons in point contacts
- 2011
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Ingår i: Low Temperature Physics. - 1063-777X. ; 37:11, s. 925-932
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Tidskriftsartikel (refereegranskat)abstract
- We investigate resonant interaction of conduction electrons with an electromagnetic field that irradiates a point contact between a ferromagnetic and a normal metal in the presence of a strong magnetic field of order 1 T. We show that electron spin-flips caused by resonant absorption and stimulated emission of photons result in a sharp peak in the magnetic-field dependence of the point-contact resistance. The height of the peak is shown to be directly proportional to the net rate of energy transfer to the electromagnetic field in the point contact due to absorption and stimulated emission of photons. Estimations indicate that our theory can serve as a basis for the explanation of recent experiments [A.M. Kadigrobov et al., New J. Phys. 13, 023007 (2011)].
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| 14. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
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Photon generation in ferromagnetic point contacts
- 2012
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Ingår i: Low temperature physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 38:12, s. 1133-1138
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Tidskriftsartikel (refereegranskat)abstract
- We show theoretically that a significant spin accumulation can occur in electric point contacts between two ferromagnetic electrodes with different magnetizations. Under appropriate conditions an inverse population of spin-split electronic levels results in stimulated emission of photons in the presence of a resonant electromagnetic field. The intensity of the emitted radiation can be several orders of magnitude higher than in typical semiconductor laser materials for two reasons. (1) The density of conduction electrons in a metal point contact is much larger than in semiconductors. (2) The strength of the coupling between the electron spins and the electromagnetic field that is responsible for the radiative spin-flip transitions is set by the magnetic exchange energy and can therefore be very large, as suggested by Kadigrobov et al. [Europhys. Lett. 67, 948 (2004)].
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| 15. |
- Krive, Ilya V., et al.
(författare)
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Resonant tunneling of electrons in quantum wires
- 2010
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 36:2, s. 119-141
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Forskningsöversikt (refereegranskat)abstract
- We consider resonant electron tunneling in various nanostructures, including single-wall carbon nanotubes, molecular transistors, and quantum wires, formed in two-dimensional electron gas. The review starts with a textbook description of resonant tunneling of noninteracting electrons through a double-barrier structure. The effects of electron-electron interaction in sequential and resonant electron tunneling are studied by using the Luttinger liquid model of electron transport in quantum wires. The experimental aspects of the problem (fabrication of quantum wires and transport measurements) are also considered. The influence of vibrational and electromechanical effects on resonant electron tunneling in molecular transistors is discussed.
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| 16. |
- Kulinich, Sergeij I., et al.
(författare)
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Nanomechanics of a magnetic shuttle device
- 2014
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Ingår i: Low temperature physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 40:10, s. 1161-1169
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Tidskriftsartikel (refereegranskat)abstract
- We show that self sustained mechanical vibrations in a model magnetic shuttle device can be driven by both the charge and the spin accumulated on the movable central island of the device. Different scenarios for how spin- and charge-induced shuttle instabilities may develop are discussed and shown to depend on whether there is a Coulomb blockade of tunneling or not. The crucial role of electronic spin flips in a magnetically driven shuttle is established and shown to cause giant magnetoresistance and dynamic magnetostriction effects.
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| 17. |
- Michelsen, Jens Harro, 1981, et al.
(författare)
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Nonadiabatic Josephson dynamics in junctions with in-gap quasiparticles
- 2010
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 36:10/11, s. 925-932 [1154-1162]-932
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Tidskriftsartikel (refereegranskat)abstract
- Conventional models of Josephson junction dynamics rely on the absence of low-energy quasiparticle states due to a large superconducting gap. With this assumption the quasiparticle degrees of freedom become «frozen out» and the phase difference becomes the only free variable, acting as a fictitious particle in a local in time Josephson potential related to the adiabatic and nondissipative supercurrent across the junction. In this article we develop a general framework to incorporate the effects of low-energy quasiparticles interacting nonadiabatically with the phase degree of freedom. Such quasiparticle states exist generically in constriction type junctions with high transparency channels or resonant states, as well as in junctions of unconventional superconductors. Furthermore, recent experiments have revealed the existence of spurious low-energy in-gap states in tunnel junctions of conventional superconductors — a system for which the adiabatic assumption typically is assumed to hold. We show that the resonant interaction with such low-energy states rather than the Josephson potential defines nonlinear Josephson dynamics at small amplitudes.
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| 18. |
- Parafilo, A., et al.
(författare)
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Nanoelectromechanics of superconducting weak links
- 2012
-
Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 38:4, s. 273-282
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Tidskriftsartikel (refereegranskat)abstract
- Nanoelectromechanical effects in superconducting weak links are considered. Three different superconducting devices are studied: (i) a single-Cooper-pair transistor, (ii) a transparent SNS junction, and (iii) a single-level quantum dot coupled to superconducting electrodes. The electromechanical coupling is due to electrostatic or magnetomotive forces acting on a movable part of the device. It is demonstrated that depending on the frequency of mechanical vibrations the electromechanical coupling could either suppress or enhance the Josephson current. Nonequilibrium effects associated with cooling of the vibrational subsystem or pumping energy into it at low bias voltages are discussed.
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| 19. |
- Parafilo, A. V., et al.
(författare)
-
Chiral effects in normal and superconducting carbon nanotube-based nanostructures
- 2010
-
Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 36:10/11, s. 959-968
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Tidskriftsartikel (refereegranskat)abstract
- The novel phenomenon of chiral tunneling in metallic single-wall carbon nanotubes is considered. It is induced by the interplay of electrostatic and pseudomagnetic effects in electron scattering in chiral nanotubes and is characterized by an oscillatory dependence of the electron transmission probability on the nanotube chiral angle and the strength of the scattering potential. The appearance of a special (Aharonov–Bohm-like) phase in chiral tunneling affects various phase-coherent phenomena in nanostructures. We examine chiral effects in: (i) persistent currents in circular nanotubes, (ii) Josephson currents in nanotube-based SNS junctions, and (iii) resonant electron tunneling through chiral nanotube-based quantum dots.
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| 20. |
- Parafilo, A. V., et al.
(författare)
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Manifestation of polaronic effects in Josephson currents
- 2013
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Ingår i: Low temperature physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 39:8, s. 685-694
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Tidskriftsartikel (refereegranskat)abstract
- Polaronic effects on the Josephson current through a vibrating quantum dot are considered. In the regime of strong electron-vibron interactions they lead to a power-law suppression of the critical current. This is manifested in an anomalous temperature dependence of the critical current at temperatures of the order of the polaronic energy shift.
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