| 1. |
- Fogel, Nina Ya., et al.
(författare)
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Direct evidence for interfacial superconductivity in two-layer semiconducting heterostructures
- 2006
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Ingår i: Physical Review B. - 1098-0121. ; 73:16
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Tidskriftsartikel (refereegranskat)abstract
- We have discovered superconductivity in the two-layer semiconducting monochalcogenide heterostrutures PbTe/PbS, PbTe/PbSe and PbTe/YbS. By comparing data from two-layer samples with data from single monochalcogenide films we conclude that the superconductivity is connected with the interface between the two semiconductors. Evidence for the low dimensional nature of the superconducting interlayer is presented and a model that explains the appearance of single-interface superconductivity is proposed.
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| 2. |
- Fogel, Nina Ya. 1938, et al.
(författare)
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Interfacial superconductivity in semiconducting monochalcogenide superlattices
- 2002
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 66:17, s. 174513(11pp.)-
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Tidskriftsartikel (refereegranskat)abstract
- Superconducting and structural properties of superconducting semiconducting multilayers are investigated. These layered systems are obtained by epitaxial growth of the isomorphic monochalcogenides of Pb, Sn, and rare-earth elements on a KCl substrate. Some of these compounds are narrow-gap semiconductors (PbTe, PbS, PbSe, SnTe). Layered structures containing one or two narrow-gap semiconductors have a metallic type of conductivity and a transition to a superconducting state at temperatures in the range of 2.56 K. Structures containing only wide-gap semiconductors (YbS, EuS, EuSe) do not demonstrate such properties. All superconducting layered systems are type-II superconductors. The critical magnetic fields and the resistive behavior in the mixed state reveal features characteristic of other layered superconductors. However, data obtained in magnetic fields testify that the period of the superstructure corresponds to half of that obtained from x-ray-diffractometry investigations. This is evidence that the superconducting layers in these samples are confined to the interfaces between two semiconductors. Electron microscopy studies reveal that in the case of epitaxial growth the interfaces contain regular grids of misfit dislocations covering all the interface area. These samples appear to undergo a superconducting transition if they have a metallic type of conductivity in the normal state. Samples with island-type dislocation grids only reveal partial superconducting transitions. The correlations between the appearance of superconductivity and the presence of dislocations, which have been found experimentally, lead to the conclusion that the normal metallic conductivity as well as the superconductivity are induced by the elastic deformation fields created by the misfit dislocation grids. A theoretical model is proposed for the description of the narrow-gap semiconductor metallization, which is due to a band inversion effect and the appearance of electron- or hole-type inversion layers near the interfaces. For different combinations of the semiconductors, such inversion layers in the superlattices can have different shapes and topology. In particular, they can form multiply connected periodic nets having a repetition period coinciding with that of the dislocation grids. Numerical estimates show that such a scenario for the appearance of superconductivity is quite likely. It is shown that the new type of metallic and superconducting nanoscale two-dimensional structures with unusual properties may be obtained from monochalcogenide semiconductors.
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| 3. |
- Ilinskaya, O. A., et al.
(författare)
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Mechanically induced thermal breakdown in magnetic shuttle structures
- 2018
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- A theory of a thermally induced single-electron 'shuttling' instability in a magnetic nano-mechanical device subject to an external magnetic field is presented in the Coulomb blockade regime of electron transport. The model magnetic shuttle device considered comprises a movable metallic grain suspended between two magnetic leads, which are kept at different temperatures and assumed to be fully spin-polarized with anti-parallel magnetizations. For a given temperature difference shuttling is found to occur for a region of external magnetic fields between a lower and an upper critical field strength, which separate the shuttling regime from normal small-amplitude 'vibronic' regimes. We find that (i) the upper critical magnetic field saturates to a constant value in the high temperature limit and that the shuttle instability domain expands with a decrease of the temperature; (ii) the lower critical magnetic field depends not only on the temperature-independent phenomenological friction coefficient used in the model but also on intrinsic friction (which vanishes in the high temperature limit) caused by magnetic exchange forces and electron tunneling between the quantum dot and the leads. The feasibility of using thermally driven magnetic shuttle systems to harvest thermal breakdown phenomena is discussed.
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| 4. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
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Hot electrons in magnetic point contacts as a photon source
- 2011
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- We propose to use a point contact between a ferromagnetic and a normal metal in the presence of a magnetic field for creating a large inverted spin population of hot electrons in the contact core. The key point of the proposal is that when these hot electrons relax by flipping their spin, microwave photons are emitted, with a frequency tunable by the applied magnetic field. While point contacts are an established technology, their use as a photon source is a new and potentially very useful application. We show that this photon emission process can be detected by means of transport spectroscopy and demonstrate stimulated emission of radiation in the 10–100 GHz range for a model point contact system using a minority-spin ferromagnetic injector. These results can potentially lead to new types of lasers based on spin injection in metals.
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| 5. |
- Shekhter, Robert I., 1947, et al.
(författare)
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Electronic spin working mechanically
- 2014
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Ingår i: Fizika Nizkikh Temperatur. - 0132-6414 .- 1816-0328. ; 40:7, s. 775-792
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Tidskriftsartikel (refereegranskat)abstract
- A single-electron tunneling (SET) device with a nanoscale central island that can move with respect to the bulk source- and drain electrodes allows for a nanoelectromechanical (NEM) coupling between the electrical current through the device and mechanical vibrations of the island. Although an electromechanical "shuttle" in-stability and the associated phenomenon of single-electron shuttling were predicted more than 15 years ago, both theoretical and experimental studies of NEM-SET structures are still carried out. New functionalities based on quantum coherence, Coulomb correlations and coherent electron-spin dynamics are of particular current interest. In this article we present a short review of recent activities in this area.
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| 6. |
- Shekhter, Robert I., 1947, et al.
(författare)
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Subwavelength terahertz spin-flip laser based on a magnetic point-contact array
- 2011
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 36:12, s. 2381-2383
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Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical design for a single-mode, truly subwavelength terahertz disk laser based on a nanocomposite gain medium comprising an array of normal-metal/ferromagnetic (FM) point contacts embedded in a thin dielectric layer. Stimulated emission of light occurs due to spin-flip relaxation of spin-polarized electrons injected from the FM side of the contacts. Ultrahigh electrical current densities in the contacts and a dielectric material with a large refractive index, neither condition being achievable in conventional semiconductor media, enables the thresholds of lasing to be overcome for the lowest-order modes of the disk, making single-mode operation possible.
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| 7. |
- Bahrova, O. M., et al.
(författare)
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Cooling of nanomechanical vibrations by Andreev injection
- 2022
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 48:6, s. 476-482
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Tidskriftsartikel (refereegranskat)abstract
- A nanoelectromechanical weak link composed of a carbon nanotube suspended between two normal electrodes in a gap between two superconducting leads is considered. The nanotube is treated as a movable single level quantum dot in which the position-dependent superconducting order parameter is induced due to the Cooper pair tunneling. We show that electron tunneling processes significantly affect the state of the mechanical subsystem. We found that at a given direction of the applied voltage between the electrodes, the stationary state of the mechanical subsystem has a Boltzmann form with an effective temperature dependent on the parameters of the device. As this takes place, the effective temperature can reach significantly small values (cooling effect). We also demonstrate that nanotube fluctuations strongly affect the dc current through the system. The latter can be used to probe the predicted effects in an experiment. Published under an exclusive license by AIP Publishing.
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| 8. |
- Bahrova, O. M., et al.
(författare)
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Nanomechanics driven by the superconducting proximity effect
- 2022
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 24:3
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Tidskriftsartikel (refereegranskat)abstract
- We consider a nanoelectromechanical weak link composed of a carbon nanotube suspended above a trench in a normal metal electrode and positioned in a gap between two superconducting leads. The nanotube is treated as a movable single-level quantum dot (QD) in which the position-dependent superconducting order parameter is induced as a result of Cooper pair tunneling. We show that in such a system, self-sustained bending vibrations can emerge if a bias voltage is applied between normal and superconducting electrodes. The occurrence of this effect crucially depends on the direction of the bias voltage and the relative position of the QD level. We also demonstrate that the nanotube vibrations strongly affect the dc current through the system, a characteristic that can be used for the direct experimental observation of the predicted phenomenon.
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| 9. |
- Gorelik, Leonid, 1952, et al.
(författare)
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Coulomb promotion of spin-dependent tunneling
- 2005
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 95:11
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Tidskriftsartikel (refereegranskat)abstract
- We study transport of spin-polarized electrons through a magnetic single-electron transistor (SET) in the presence of an external magnetic field. Assuming the SET to have a nanometer size central island with a single-electron level we find that the interplay on the island between coherent spin-flip dynamics and Coulomb interactions can make the Coulomb correlations promote rather than suppress the current through the device. We find the criteria for this new phenomenon-Coulomb promotion of spin-dependent tunneling-to occur. © 2005 The American Physical Society.
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| 10. |
- Gorelik, Leonid, 1952, et al.
(författare)
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Giant shot noise due to mechanical transportation of spin-polarized electrons
- 2008
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Ingår i: Physical Review B. - 1098-0121. ; 77:17, s. 174304-
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Tidskriftsartikel (refereegranskat)abstract
- We show that single-electron "shuttling" of electrons in a magnetic nanoelectromechanical single-electron transistor device can be an efficient tool for studying electron spin-flip relaxation on quantum dots. The reason is traced to a spin blockade of the mechanically aided shuttle current that occurs in devices with highly polarized and collinearly magnetized leads. This results in giant peaks in the shot-noise spectral function, wherein the peak heights are only limited by the rate of electronic spin flips. Therefore, we show that nanomechanical spectroscopy of the spin-flip rate is possible, allowing spin-flip relaxation times as long as 10 mu s to be detected.
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