| 1. |
- Bergholtz, Emil Johansson, et al.
(författare)
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Quantum Hall hierarchy wave functions: From conformal correlators to Tao-Thouless states
- 2008
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 77:16, s. 165325-1-165325-9
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Tidskriftsartikel (refereegranskat)abstract
- Laughlin’s wave functions, which describe the fractional quantum Hall effect at filling factorsν=1/(2k+1), can be obtained as correlation functions in a conformal field theory, and recently, this construction was extended to Jain’s composite fermion wave functions at filling factors ν=n/(2kn+1). Here, we generalize this latter construction and present ground state wave functions for all quantum Hall hierarchy states that are obtained by successive condensation of quasielectrons (as opposed to quasiholes) in the original hierarchy construction. By considering these wave functions on a cylinder, we show that they approach the exact ground states, which are the Tao-Thouless states, when the cylinder becomes thin. We also present wave functions for the multihole states, make the connection to Wen’s general classification of Abelian quantum Hall fluids, and discuss whether the fractional statistics of the quasiparticles can be analytically determined. Finally, we discuss to what extent our wave functions can be described in the language of composite fermions.
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| 2. |
- Christie, Michael, 1946, et al.
(författare)
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Gender bias in engineering education
- 2006
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Ingår i: Shifting paradigms in Engineering Education; publ. Chalmers Strategic Effort on Learning and Teaching (C-SELT), Chalmers University of Technology, Göteborg. ; , s. 279-287
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Hansson, Thors Hans, et al.
(författare)
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Conformal Field Theory Approach to Abelian and Non-Abelian Quantum Hall Quasielectrons
- 2009
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 102:16, s. 166805-1-166805-4
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Tidskriftsartikel (refereegranskat)abstract
- The quasiparticles in quantum Hall liquids carry fractional charge and obey fractional quantum statistics. Of particular recent interest are those with non-Abelian statistics, since their braiding properties could, in principle, be used for robust coding of quantum information. There is already a good theoretical understanding of quasiholes in both Abelian and non-Abelian quantum Hall states. Here we develop conformal field theory methods that allow for an equally precise description of quasielectrons and explicitly construct two- and four-quasielectron excitations of the non-Abelian Moore-Read state.
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| 4. |
- Hansson, Thors Hans, et al.
(författare)
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Quantum Hall quasielectron operators in conformal field theory
- 2009
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 80:16, s. 165330-1-165330-22
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Tidskriftsartikel (refereegranskat)abstract
- In the conformal field theory (CFT) approach to the quantum Hall effect, the multielectron wave functions are expressed as correlation functions in certain rational CFTs. While this approach has led to a well-understood description of the fractionally charged quasihole excitations, the quasielectrons have turned out to be much harder to handle. In particular, forming quasielectron states requires nonlocal operators, in sharp contrast to quasiholes that can be created by local chiral vertex operators. In both cases, the operators are strongly constrained by general requirements of symmetry, braiding, and fusion. Here we construct a quasielectron operator satisfying these demands and show that it reproduces known good quasiparticle wave functions, as well as predicts additional ones. In particular, we propose explicit wave functions for quasielectron excitations of the Moore-Read Pfaffian state. Further, this operator allows us to explicitly express the composite fermion wave functions in the positive Jain series in hierarchical form, thus settling a long-time controversy. We also critically discuss the status of the fractional statistics of quasiparticles in the Abelian hierarchical quantum Hall states and argue that our construction of localized quasielectron states sheds new light on their statistics. At the technical level we introduce a generalized normal ordering that allows us to “fuse” an electron operator with the inverse of an hole operator and also an alternative approach to the background charge needed to neutralize CFT correlators. As a result we get a fully holomorphic CFT representation of a large set of quantum Hall wave functions.
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| 5. |
- Jonsson, Magnus, 1979, et al.
(författare)
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Effects of short range forces on a three-terminal nanorelay
- 2003
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Ingår i: Fullerenes vol. 13 -- Fullerenes and Nanotubes: The Building Blocks of Next Generation Nanodevices. - 1566773970 ; , s. 432-439
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We have performed a theoretical analysis of the operational characteristics of a carbon-nanotube-based three-terminal nanorelay. In the present study we focus on introducing short range forces into the model. We show is that these forces have a significant impact on the characteristics of the relay. We also investigate the nanorelay as a memory element, and conclude that this is a promising application.
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| 6. |
- Jonsson, Magnus, 1979, et al.
(författare)
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Effects of surface forces and phonon dissipation in a three-terminal nanorelay
- 2004
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Ingår i: Journal of Apllied Physics. ; 96, s. 629-
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Tidskriftsartikel (refereegranskat)abstract
- We have performed a theoretical analysis of the operational characteristics of a carbonnanotube-based three-terminal nanorelay. We show that short range and van der Waals forces have a significant impact on the characteristics of the relay and introduce design constraints. We also investigate the effects of dissipation due to phonon excitation in the drain contact, which changes the switching time scales of the system, decreasing the longest time scale by 2 orders of magnitude. We show that the nanorelay can be used as a memory element and investigate the dynamics and properties of such a device.
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| 7. |
- Viefers, Susanne, 1970, et al.
(författare)
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ELECTROMECHANICAL NANOTUBE TUNNELING DEVICE COMPRISING SOURCE, DRAIN AND GATE
- 2011
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- The present invention relates to a nanotube device (100) comprising a nanotube with a longitudinal and a lateral extension, a structure for supporting at least a first part of the nanotube, and first means for exerting a force upon the nanotube in a first direction defined by its lateral extension. At least a second part of the nanotube protrudes beyond the support of said structure, so that when said force exceeds a certain level, the second part of the nanotube will flex in the direction of its lateral extension, and thereby close a first electrical circuit. Suitably, the first means for exerting said force upon the nanotube is an electrical means, the force being created by applying a voltage to the means. The device allows for quantum mechanics tunnel effects, both at a source and at a drain electrode.
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| 8. |
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| 9. |
- Viefers, Susanne, 1970, et al.
(författare)
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Gender equity in higher education: why and how? A case study of gender issues in a science faculty
- 2006
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Ingår i: European Journal of Engineering Education. - : Informa UK Limited. - 0304-3797 .- 1469-5898. ; 31:1, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- At a time when more and more natural science subjects are attracting an increasing number of women (chemistry for example) physics remains a male stronghold. It is not easy to understand this phenomenon or the anomaly that over-representation of males in physics faculties is more likely to occur in countries known for their attempts at equalizing opportunities for women, Sweden, for example, has a parliament in which 40% of its members are women and yet the average percentage of women lecturers in physics faculties is about half of that. In Sweden today women professors of physics (both appointed and promoted) typically represent 10% or less of the total professorial staff. In this paper we report on a qualitative case study of gender equity in a large physics faculty in a Swedish university. In order to locate our study in a more general social and political context we look at Swedish legislation that seeks to equalize opportunities for women in higher education. The rest of the study focuses on a brief review of research in the area of gender issues in higher education and an analysis of interviews with three women in physics: one a professor, one a lecturer and the third a PhD student. The analysis discusses why the current disproportion exists, if it is a good or bad thing for physics and physicists and how one might rectify any perceived problems in terms or gender relations and gender equity.
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| 10. |
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| 11. |
- Viefers, Susanne, 1970, et al.
(författare)
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Nanotube relay device
- 2007
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Patent (övrigt vetenskapligt/konstnärligt)
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