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  • 1.
    Bankel, Johan
    et al.
    Chalmers University of technology, Göteborg.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Engström, Madelaine
    Linköping University, The Institute of Technology.
    Wiklund, Ingela
    Linköping University, The Institute of Technology.
    Crawdley, Edward F
    Massachusetts Institute of Technology, USA.
    Soderholm, Diane
    Massachusetts Institute of Technology, USA.
    Gaidi, Khalid El
    KTH, Stockholm.
    Östlund, Sören
    KTH, Stockholm.
    Benchmarking engineering Curricula with the CDIO Syllabus*2005In: International journal of engineering education, ISSN 0949-149X, Vol. 21, no 1, p. 121-133Article in journal (Refereed)
  • 2.
    Bengtsson, Olof
    et al.
    IFM Linköpings universitet.
    Larsson, Johan
    IFM Linköpings universitet.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Emulation of quantum mechanical billiards by electrical resonance circuits2005In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 71, p. 056206-1-056206-6Article in journal (Refereed)
  • 3.
    Berdyugina, Svetlana
    et al.
    Kiepenheuer Institut für Sonnenphysik, Freiburg, Tyskland.
    Harvey, Jack
    National Solar Observatory, Tuscon, Arizona, USA.
    Solanki, Sami
    Max Planck Institute for Solar System Research, Katlenburg-Lindau, Tyskland.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Edvardsson, David
    Vetenskapsrådet, Swedish Research Council.
    Assessment of Expressions-of-interests for hosting the Institute for Solar Physics - Panel's report2011Report (Other academic)
  • 4.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    All-Time High2010In: Fysikaktuellt, ISSN 0283-9148, no 4, p. 3-3Article in journal (Other (popular science, discussion, etc.))
  • 5.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Dimensional crossover in semiconductor structures: From2006In: International School/Workshop Charge and spin effects at the nanoscale,2006, 2006Conference paper (Other academic)
    Abstract [en]

         

  • 6.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Dimensional Crossover in Semiconductor Structures: From 3D Electron Transport to Ballistic Electrons in 1D2006In: Turkish journal of physics, ISSN 1300-0101, Vol. 30, p. 197-212Article in journal (Refereed)
  • 7.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Drottningen och filosofen - mötet mellan Christina och Descartes2013In: Fysikaktuellt, ISSN 0283-9148, no 3, p. 22-22Article, book review (Other (popular science, discussion, etc.))
  • 8.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Entanglement väcker språkdebatt2010In: Fysikaktuellt, ISSN 0283-9148, no 2, p. 5-5Article in journal (Refereed)
  • 9.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Fortsatt förtroende - Fysikaktuellt nr 12012Other (Other (popular science, discussion, etc.))
  • 10.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Fysik2012In: Naturvetarguiden / [ed] Marita Teräs, Nacka: Naturvetarna , 2012, 1, , p. 141Chapter in book (Other (popular science, discussion, etc.))
  • 11.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics.
    Förolämpande och konspiratorisk - debattinlägg2005In: Sydsvenska Dagbladet, Vol. 28 maj 2005, p. C2-C3Article in journal (Other (popular science, discussion, etc.))
  • 12.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics.
    Gärna en debatt men håll den saklig - Debattinlägg2006In: Sydsvenska Dagbladet, ISSN 1104-0068, Vol. 2006-01-12Article in journal (Other (popular science, discussion, etc.))
  • 13.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Hur förstår man fysik?2010In: Fysikaktuellt, no 3, p. 3-3Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    n/a

  • 14.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Hur står det till med SFS?2011In: Fysikaktuellt, ISSN 0283-9148, no 4, p. 5-5Article in journal (Other (popular science, discussion, etc.))
  • 15.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    International evaluation of the Swedish polar research organization2008Report (Other academic)
    Abstract [en]

      

  • 16.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Jakten på liv i universum2013In: Fysikaktuellt, ISSN 0283-9148, no 4, p. 26-26Article, book review (Other (popular science, discussion, etc.))
  • 17.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    NSC during 20 years2009Conference paper (Other academic)
  • 18.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Parallella världar - Fysikaktuellt nr 22012Other (Other (popular science, discussion, etc.))
  • 19.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Promoveringsskrift våren 20072007Other (Other (popular science, discussion, etc.))
  • 20.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Signerat: Nya krafter vid rodret2012In: Fysikaktuellt, ISSN 0283-9148, no 4, p. 3-3Article in journal (Other (popular science, discussion, etc.))
  • 21.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Signerat; Välkommen till år 20102010In: Fysikaktuellt, ISSN 0283-9148, no 1, p. 3-3Article in journal (Other (popular science, discussion, etc.))
  • 22.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Slow physics2012In: Fysikaktuellt, ISSN 0283-9148, no 3, p. 3-3Article in journal (Other (popular science, discussion, etc.))
  • 23.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Spännande program på Nordiska Fysikdagarna2011In: Fysikaktuellt, ISSN 0283-9148, no 2, p. 21-21Article in journal (Other (popular science, discussion, etc.))
  • 24.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    The story of Cray number nine2008Other (Other (popular science, discussion, etc.))
    Abstract [en]

      

  • 25.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Åsikter om infrastruktursatsningarna2012In: Fysikaktuellt, ISSN 0283-9148, no 3, p. 5-5Article in journal (Other (popular science, discussion, etc.))
  • 26.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Maksimov, Dmitrii N.
    L.V. Kirensky Institute of Physics.
    Sadreev, Almas F.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Höhmann, Ruven
    AG Quantenchaos.
    Kuhl, Ulrich
    AG Quantenchaos.
    Stöckmann, Hans-Jürgen
    AG Quantenchaos.
    Quantum stress in chaotic billiards2008In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 77, no 066209Article in journal (Refereed)
    Abstract [en]

    This paper reports on a joint theoretical and experimental study of the Pauli quantum-mechanical stress tensor T(x,y) for open two-dimensional chaotic billiards. In the case of a finite current flow through the system the interior wave function is expressed as =u+iv. With the assumption that u and v are Gaussian random fields we derive analytic expressions for the statistical distributions for the quantum stress tensor components T. The Gaussian random field model is tested for a Sinai billiard with two opposite leads by analyzing the scattering wave functions obtained numerically from the corresponding Schrödinger equation. Two-dimensional quantum billiards may be emulated from planar microwave analogs. Hence we report on microwave measurements for an open two-dimensional cavity and how the quantum stress tensor analog is extracted from the recorded electric field. The agreement with the theoretical predictions for the distributions for T(x,y) is quite satisfactory for small net currents. However, a distinct difference between experiments and theory is observed at higher net flow, which could be explained using a Gaussian random field, where the net current was taken into account by an additional plane wave with a preferential direction and amplitude.

  • 27.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Albrow, Michael
    Fermi National Lab.
    Grenier, Isabelle
    CEA U Paris VII.
    Bedell, Kevin
    Boston College.
    Schwalm, Dirk
    Max Planck Institute for Nuclear Physics.
    Focusing on Quality; Panel 3: Physics, Theoretical Physics2008Report (Other academic)
    Abstract [en]

      

  • 28.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Carlile, Colin
    Carlsson, Patrik
    Lunds universitet.
    Sverige rustar för neutronkamp2007In: Fysikaktuellt, ISSN 0283-9148, no 3, p. 14-15Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

       

  • 29.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Cederwall, Martin
    Chalmers.
    Forssell-Aronsson, Eva
    Sahlgrenska akademin.
    Fredriksson, Billy
    Vetenskapsrådets ämnesråd för naturvetenskap och teknik.
    Goksör, Mattias
    Göteborgs universtitet.
    Häggström, Olle
    Chalmers.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Mårtensson, Ann-Sofie
    Högskolan i Borås.
    Sandelius, Anna Stina
    Göteborgs universitet.
    Wennberg, Ann-Marie
    Sahlgrenska universitetssjukhuset.
    Stärk matematiken och naturvetenskapen i nya gymnasiet2010In: NyTeknikArticle in journal (Other (popular science, discussion, etc.))
  • 30.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Fors, Cecilia
    Fysikersamfundet 90 år2010In: Fysikaktuellt, ISSN 0283-9148, no 2, p. 12-12Article in journal (Other (popular science, discussion, etc.))
  • 31.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Svensson, Tomas
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Wiklund, Ingela
    Linköping University, The Institute of Technology.
    The Development of the Applied Physics and Electrical Engineering (Y) Programme at Linköping University through Participation in the CDIO Initiative2005In: Proceedings of the 8th UICEE Annual Conference on Engineering Education, 2005, p. 321-324Conference paper (Refereed)
  • 32.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Hallonsten, Olof
    Göteborgs universitet.
    Timeline of major events2012In: In pursuit of a promise: Perspectives on the political process to establish the European Spallation Source (ESS) in Lund, Sweden / [ed] Olof Hallonsten, Arkiv förlag & tidskrift, 2012, p. 21-30Chapter in book (Other academic)
    Abstract [en]

    On 28 May 2009, at a closed meeting in Brussels, ministers and state secretaries of education and science from several EU countries decided to build the European Spallation Source (ESS) in Lund, Sweden. Or did they?It is common for big European science projects to be surrounded by secrecy and political deceit, but the ESS is extraordinary in its elusiveness. There is a remarkable lack of concrete economic, political, technical and scientific underpinnings to the project  but a boasting certainty in the promises of future paybacks.The ESS is an accelerator-based neutron spallation facility that will cost billions of Euros to build and run. It is expected to bring new knowledge in several fields including materials science, energy research, and the life sciences. But its financing is not yet certain, and future returns hard to predict. How then could the decision to build ESS occur? Why was there so little organized resistance?This book places the ESS project in its political and scientific context. It links the decisions taken to the history of Big Science in Europe and in Sweden. It looks at the dynamic political processes of establishing this megaproject in a small town in the south of Sweden. The eight chapters start from a paradoxical state of affairs: The ESS is not funded, and not formally decided in any binding agreements  yet it is treated as a future reality, locally and nationally, loaded with promises of scientific, economic and social returns.The book makes a much-needed first contribution to the analysis of the ESS project and its political, environmental, and social ramifications. It should be read by scholars of science and technology studies, politicians and the interested general public.

  • 33.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Irina I., Yakimenko
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Basic Modeling of Openness, Quantum States and Transport in Two- and Three-Dimensional Ballistic Cavities2010In: Journal of Siberian Federal University. Mathematics & Physics, Vol. 3, p. 280-288Article in journal (Refereed)
    Abstract [en]

    A basic model for particle states and current flow in open quantum dots/billiards are investigated. The model is unconventional and extends the use of complex potentials first introduced in phenomenological nuclear inelastic scattering theory (the optical model). Attached leads/source drain are represented by complex potentials. Probability densities and currents flows for open 2D quantum dots/billiards are calculated and the results are compared with microwave measurements used to emulate the dot. We also apply the model to a recangular enclosure and report on helical flows guided by nodal lines and disc-like accumulations of flow lines. The model is of conceptual as well as practical and educational interest.

  • 34.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Jaksch, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Yakymenko, Iryna
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Effects of electron interactions at crossings of Zeeman-split subbands in quantum wires2005Article in journal (Refereed)
    Abstract [en]

    Recent experimental studies of Zeeman-split one-dimensional subbands in ballistic quantum wires in an in-plane magnetic field show that additional nonquantized conductance structures occur as subbands cross at low electron densities [A. C. Graham et al., Phys. Rev.Lett. 91, 136404 (2003)]. These structures are called 0.7 analogs. We analyze the experimental transconductance data within the Kohn-Sham spin-density-functional method, including exchange and correlation effects for an infinite split-gate quantum wire in a parallel, in-plane magnetic field B∥. Energy levels are found to rearrange abruptly as they cross due to polarization effects driven by exchange and Coulomb interactions. Experimental qualitative features are explained well by this model. ©2005 The American Physical Society.

  • 35.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Larsson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Bengtsson, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Electrical Resonance Circuits as Analogs to Quantum Mechanical Billiards2006In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 109, p. 33-42Article in journal (Refereed)
    Abstract [en]

    We propose that a two-dimensional electric network may be used for fundamental studies of wave function properties, transport, and related statistics. Using Kirchhoff 's current law and the jw-method we find that the network is analogous to a discretized Schrodinger equation for quantum billiards and clots. Thus the complex electric potentials play the role of quantum rnechanical wave functions.

  • 36.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Ljung, P.
    Siemens Corporate Research.
    Nature of streamlines for Berry-type wave functions in open 3D cavities2009In: MATHEMATICAL MODELING OF WAVE PHENOMENA, American Institute of Physics (AIP), 2009, Vol. 1106, p. 253-259Conference paper (Refereed)
    Abstract [en]

    We explore preliminary a 3D wave cavity in which the interior complex wave functions are of Berry-type. Streamlines and novel disc-like features are uncovered by means of selective and interactive visualization.

  • 37.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Ljung, Patric
    Siemens Corporate Research, USA.
    Nature of Streamlines for Berry-type Wave Functions in Open 3D Cavities2008In: Radio Science and Communications Mathematical Modelling of Wave Phenomena,2008, 2008, p. 41-42Conference paper (Refereed)
    Abstract [en]

      

  • 38.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Malm, M
    Wärnsby, M
    Sjöberg, M
    ESS - European Spallation Source – tillstånd för miljö och utveckling2009Conference paper (Other academic)
  • 39.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Matic, Aleksandar
    Chalmers tekniska högskola, Göteborg.
    Science at the ESS: a brief outline2012In: In Pursuit of a Promise: Perspectives on the political process to establish the European Spallation Source (ESS) in Lund, Sweden / [ed] Olof Hallonsten, Arkiv förlag & tidskrift, 2012, p. 31-47Chapter in book (Other academic)
    Abstract [en]

    On 28 May 2009, at a closed meeting in Brussels, ministers and state secretaries of education and science from several EU countries decided to build the European Spallation Source (ESS) in Lund, Sweden. Or did they?It is common for big European science projects to be surrounded by secrecy and political deceit, but the ESS is extraordinary in its elusiveness. There is a remarkable lack of concrete economic, political, technical and scientific underpinnings to the project  but a boasting certainty in the promises of future paybacks.The ESS is an accelerator-based neutron spallation facility that will cost billions of Euros to build and run. It is expected to bring new knowledge in several fields including materials science, energy research, and the life sciences. But its financing is not yet certain, and future returns hard to predict. How then could the decision to build ESS occur? Why was there so little organized resistance?This book places the ESS project in its political and scientific context. It links the decisions taken to the history of Big Science in Europe and in Sweden. It looks at the dynamic political processes of establishing this megaproject in a small town in the south of Sweden. The eight chapters start from a paradoxical state of affairs: The ESS is not funded, and not formally decided in any binding agreements  yet it is treated as a future reality, locally and nationally, loaded with promises of scientific, economic and social returns.The book makes a much-needed first contribution to the analysis of the ESS project and its political, environmental, and social ramifications. It should be read by scholars of science and technology studies, politicians and the interested general public.

  • 40.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Ouchterlony, T
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Chaos in a quantum dot with spin-orbit coupling2001In: Foundations of physics, ISSN 0015-9018, E-ISSN 1572-9516, Vol. 31, no 2, p. 233-242Article in journal (Refereed)
    Abstract [en]

    Level statistics are nodal point distribution in a rectangular semiconductor quantum dot are studies for different degrees of spin-orbit coupling. The chaotic features occurring from the spin-orbit coupling have no classical counterpart. Using experimental values of GaSb/InAs/GaSb semiconductor quantum wells we find that level repulsion can lead to the semi-Poisson distribution for nearest level separations. Nodal lines and nodal points are also investigated. Comparison is made with nodal point distributions for fully chaotic states.

  • 41.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Pepper, M
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Cavendish Lab, Semicond Phys Grp, Cambridge CB3 0HE, England Toshiba Res Europe, Cambridge Res Lab, Cambridge CB4 0WE, England TeraView Ltd, Cambridge CB4 0WE, England.
    New directions with fewer dimensions2002In: Physics world, ISSN 0953-8585, Vol. 15, no 10, p. 37-42Article in journal (Refereed)
  • 42.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Pepper, Michael
    University College London.
    Electrons in one dimension2010In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 368, p. 1141-1162Article, review/survey (Refereed)
    Abstract [en]

    In this article, we present a summary of the current status of the study of the transport of electrons confined to one dimension in very low disorder GaAs–AlGaAs heterostructures. By means of suitably located gates and application of a voltage to ‘electrostatically squeeze’ the electronic wave functions, it is possible to produce a controllable size quantization and a transition from two-dimensional transport. If the length of the electron channel is sufficiently short, then transport is ballistic and the quantized subbands each have a conductance equal to the fundamental quantum value 2e2/h, where the factor of 2 arises from the spin degeneracy. This mode of conduction is discussed, and it is shown that a number of many-body effects can be observed. These effects are discussed as in the spin-incoherent regime, which is entered when the separation of the electrons is increased and the exchange energy is less than kT. Finally, results are presented in the regime where the confinement potential is decreased and the electron configuration relaxes to minimize the electron–electron repulsion to move towards a two-dimensional array. It is shown that the ground state is no longer a line determined by the size quantization alone, but becomes two distinct rows arising from minimization of the electrostatic energy and is the precursor of a two-dimensional Wigner lattice.

  • 43.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Persson, Bengt
    Linköping University, Department of Physics, Chemistry and Biology, Bioinformatics . Linköping University, The Institute of Technology.
    20 years in HPC 1989-20092009Other (Other (popular science, discussion, etc.))
  • 44.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Petersen, H.K.
    Thiede, J.
    Rapport - International evaluation of the Swedish organization of polar research (Swedish Research Council)2007Other (Other (popular science, discussion, etc.))
    Abstract [en]

        

  • 45.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Sadreev, A.F.
    Kirensky Institute of Physics, 660036, Krasnoyarsk, Russian Federation.
    Starikov, Anton
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Quantum chaos among nodal points and streamlines at ballistic electron transport through open quantum dots2001In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 12, no 4, p. 562-565Conference paper (Other academic)
    Abstract [en]

    We trace signatures of quantum chaos in the distribution of nodal points and streamlines for coherent electron transport through different types of quantum dots (chaotic and regular). We have calculated normalized distribution functions for the nearest distances between nodal points and found that this distribution may be used as a signature of quantum chaos for electron transport in open systems. Different chaotic billiards show the same characteristic distribution function for nodal points. This signature of quantum chaos is well reproduced using well known approaches for chaotic wavefunctions. We have also investigated the quantum flows which display some remarkable features.

  • 46.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Sadreev, Almas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Starikov, Anton
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Crossover from regular to irregular behavior in current flow through open billiards2002In: Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, Vol. 66, no 1Article in journal (Refereed)
    Abstract [en]

    We discuss signatures of quantum chaos in terms of distributions of nodal points, saddle points, and streamlines for coherent electron transport through two-dimensional billiards, which are either nominally integrable or chaotic. As typical examples of the two cases we select rectangular and Sinai billiards. We have numerically evaluted distribution functions for nearest distances between nodal points and found that there is a generic form for open chaotic billiards through which a net current is passed. We have also evaluated the distribution functions for nodal points with specific vorticity (winding number) as well as for saddle points. The distributions may be used as signatures of quantum chaos in open systems. All distributions are well reproduced using random complex linear combinations of nearly monochromatic states in nominally closed billiards. In the case of rectangular billiards with simple sharp-cornered leads the distributions have characteristic features related to order among the nodal points. A flaring or rounding of the contact regions may, however, induce a crossover to nodal point distributions and current flow typical for quantum chaos. For an irregular arrangement of nodal points, as for example in the Sinai billiard, the quantum flow lines become very complex and volatile, recalling chaos among classical trajectories. Similarities with percolation are pointed out. ©2002 The American Physical Society.

  • 47.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Yakimenko, II
    Effects of exchange and electron correlation on conductance and nanomagnetism in ballistic semiconductor quantum point contacts2002In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, no 8Article in journal (Refereed)
    Abstract [en]

    The spontaneous magnetization of a quantum point contact (QPC) formed between two large quantum dots by a lateral confinement of a high-mobility two-dimensional electron gas is studied for a realistic GaAs/AlxGa1-xAs heterostructure. The model of the device incorporates the contributions from a patterned gate, doping, surface states, and mirror charges. To explore the magnetic properties, the Kohn-Sham local spin-density formalism is used with exchange and correlation potentials that allows for local spin polarization. Exchange is the dominant mechanism behind local magnetization within the QPC, while the correlation part is less prominent. However, the correlation potential gives rise to an important correction in the QPC potential. Below the first conduction plateau we thus find a magnetized regime corresponding approximately to a single electron spin. Using an approximate separable saddle potential we compute the conductance and recover the so-called similar to0.7 (2e(2)/h) conduction anomaly plus an additional anomaly at similar to0.4 (2e(2)/h) below which the magnetization collapses.

  • 48.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Yakimenko, I.I.
    Bychkov, A.M.
    Centre for Quantum Computation, Clarendon Laboratory, Oxford OX1 3PU, United Kingdom, Moscow State Engineering Physics Institute, Technical University, 115409 Moscow, Russian Federation.
    On the role of electron exchange and correlation in semiconductor quantum dots2001In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 12, no 4, p. 529-532Conference paper (Other academic)
    Abstract [en]

    Spontaneous magnetization of single and coupled quantum dots formed by lateral confinement of a high-mobility two-dimensional electron gas is studied for a realistic GaAs/AlGaAs heterostructure. The modelling of the device takes into account contributions from a patterned gate, doping, surface states, and mirror charges. To explore the magnetic properties we use the Kohn-Sham local spin-density formalism including the contributions from electron correlation and exchange. We show by explicit calculations that the exchange is the dominant mechanism driving a spontaneous magnetization of a dot. The correlation potential reduces the amount of level splitting and usually affects the electron content in the dot at a given gate voltage. These effects are, however, small and may be neglected under present circumstances. Single dots with up to 50 electrons have been studied.

  • 49.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Yakimenko, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Basic Modeling of Openess, Quantum States and Transport in Two- and Three-Dimensional Ballistic Cavities2009In: Basic Modeling of Openess, Quantum States and Transport in Two- and Three-Dimensional Ballistic Cavities, 2009Conference paper (Refereed)
  • 50.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Yakimenko, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Hakanen, Jani
    Ericsson AB.
    Modeling of open quantum dots and wave billiards using imaginary potentials for the source and the sink2010In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 12, no 073005Article in journal (Refereed)
    Abstract [en]

    A heuristic model for particle states and current flow in open ballistictwo-dimensional (2D) quantum dots/wave billiards is proposed. The modelmakes use of complex potentials first introduced in phenomenological nuclearinelastic scattering theory (the optical model). Here we assume that externalinput and output leads connecting the system to the source and the drain regionsmay be represented by complex potentials. In this way, a current may be set upbetween the two ‘pseudo-leads’. Probability densities and current flows for anopen quantum dot are analyzed here numerically and the results are comparedwith the microwave measurements used to emulate the system. The model isof conceptual as well as practical interest. In addition to quantum billiards, itmay be used as a tool per se to analyze transport in classical wave analogues,such as microwave resonators, acoustic resonators, effects of leakage on suchsystems, etc.

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