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- 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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| 2. |
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| 3. |
- Krive, Ilya V., et al.
(författare)
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Charge and spin effects in mesoscopic Josephson junctions
- 2004
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Ingår i: Fizika Nizkikh Temperatur (Kharkov). - 0132-6414. ; 30, s. 554-
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Tidskriftsartikel (refereegranskat)abstract
- We consider the charge and spin effects in low dimensional superconducting weak, links. The first part of the review deals with the effects of electron - electron interaction in Superconductor/Luttlnger liquid/Superconductor junctions. The experimental realization of this mesoscopic hybrid system can be the individual single wall carbon nanotube that bridges the gap between two bulk superconductors. The dc Josephson current through a Luttinger liquid is evaluated in the limits of perfectly and poorly transmitting junctions. The relationship between the Josephson effect in a long SNS junction and the Casimir effect is discussed. In the second part of the paper we review the recent results concerning the influence of the Zeeman and Rashba interactions on the thermodynamical properties of ballistic S-QW-S junction fabricated in two dimensional electron gas. It is shown that in magnetically controlled junction there are conditions for resonant Cooper pair transition which results in giant supercurrent through a tunnel junction and a giant magnetic response of a multichannel SNS junction. The supercurrent induced by the joint action of the Zeeman and Rashba interactions in 1D quantum wires connected to bulk superconductors is predicted.
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| 4. |
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| 6. |
- Bohgard, Mats, et al.
(författare)
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Pedagogisk förändring av arbetsvetenskapskurser i några olika utbildningsprogram vid LTH
- 2003
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Ingår i: Pedagogisk inspirationskonferens LTH 27 maj 2003. - Lund : Lunds tekniska högskola, Lunds universitet. ; , s. 14-17
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Konferensbidrag (refereegranskat)abstract
- Vi har genomfört genomgripande förändringar i obligatoriska grundkurser i arbetsvetenskap. Förändringarna har genomförts som en utvecklingsprocess i vilken samtliga lärare som deltagit i kurserna har medverkat. Processen startade med konsulthjälp från Universitetspedagogiskt centrum vid Lunds universitet, fortsatte med kompetensutveckling av oss själva och följdes av några utvecklingsprojekt, varefter från grunden förändrade kurser genomfördes under fyra år. Den nya uppläggningen medförde att vi fick positiva attityder i studentenkäterna när det gällde två av kurserna i årskurs 2 i vilken medodiken genomfördes fullständigt. I en kurs, som gavs i årskurs 1 och i vilken den nya uppläggningen endast delvis genomfördes blev studentattityderna negativa.
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| 7. |
- Cherkasov, A. R., et al.
(författare)
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Correlation analysis in the chemistry of free radicals
- 2001
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Ingår i: Uspehi himii. - 0042-1308 .- 1817-5651. ; 70:1, s. 3-27
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Forskningsöversikt (refereegranskat)abstract
- Published data available by now on the use of correlation analysis in the free-radical chemistry are discussed systematically. The scales of <> sigma -constants of substituents proposed previously are analysed. It is shown that none of them is suitable as a general scale because almost in all cases, it is impossible to separate correctly the proper radical and polar contributions to the overall effect of substituents. A new approach to the quantitative estimation of the relationship between the structure and reactivity of molecules in free-radical processes is proposed and called r(-2)-analysis.
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| 8. |
- Clague, JJ, et al.
(författare)
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Late Holocene environmental change at treeline in the Northern Coast Mountains, British Columbia, Canada
- 2004
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 23:23-24, s. 2413-2431
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Tidskriftsartikel (refereegranskat)abstract
- An integrated stratigraphic, paleoecological, and geochronological study of lake and fen sediments just beyond the terminus of Berendon Glacier provides insights into late Holocene climate, vegetation, and glacier change in the northern Coast Mountains of British Columbia. Cores collected from two small lakes in the foreland of Berendon Glacier and pits dug in a nearby fen record Little lee Age and older glacier advances. The first Little Ice Age advance in this area began more than 500 years ago and peaked in the early 17th century. An earlier Neoglacial advance began about 2800-3000 cal yr ago and may have lasted for hundreds of years. There is also evidence for an intervening advance of even smaller magnitude around 1200-1300 cal yr ago. The advances are broadly synchronous with those in other parts of western North America, indicating that they were caused by regional, possibly global, changes in climate. Plant communities within the study area did not change dramatically during the late Holocene. The ranges of some plants, however, likely retracted or extended near treeline in response to changes in mean temperatures of perhaps 1-2degreesC, as A well as changes in summer snow cover. The greatest changes in vegetation occurred within and just beyond the forefields of Berendon, Frank Mackie, and other nearby glaciers. The largest climate shifts of the last 3000 years took place during the late Little Ice Age and the last century. Climate warmed about 1-2degreesC during the 20th century, accompanied by a rise in treeline, an increase in coniferous tree cover in the subalpine zone, and an increase in the temperature and biological productivity of ponds. These trends are likely to continue if climate, as expected, continues to warm. (C) 2004 Elsevier Ltd. All rights reserved.
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| 9. |
- Erell, E, et al.
(författare)
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"SOLVENT": development of a reversible solar-screen glazing system
- 2004
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 36:5, s. 467-480
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Tidskriftsartikel (refereegranskat)abstract
- Preliminary experiments with a novel glazing system developed at the Desert Architecture and Urban Planning Unit of Ben-Gurion University of the Negev in Israel indicated that it may provide improved visual and thermal performance in buildings with large glazed areas located in sunny regions, regardless of orientation. In winter, it reduces glare, local over-heating and damage to furnishings caused by exposure to direct solar radiation, with only a small reduction in solar space heating. In summer, it reduces the penetration of unwanted radiation without obstructing the view through the window, to an extent that may render external shading devices unnecessary. The SOLVENT project was contracted to complete the development of the glazing system, which is based on the concept of converting short-wave solar radiation to convective heat and long wave radiation. The glazing system was modeled and evaluated experimentally; a suitable frame was developed for it; and a design tool required for its application was developed. The current paper reports on physical modeling and experimental evaluation of the glazing system.
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