There are three major activities at the Niels Bohr Institute, Nano-Science Center:

1. Study of single electron transmission through a GaAlAs heterostructure quantum point contact using surface acoustic waves at f=3 GHz. At 4.2 K we observe current quantization at the values fe, 2fe, 3fe, ..We are working on a device where these electrons are dumped in a p-region to recombine and emit a single photon light puls. A major challenge is to form a lateral p-i-n diode with a reliable backgate. This work is ongoing.

   
   

2. Investigate the resistance through carbon nanotubes, where the contacts are either made of gold, titanium or iron. We are looking at Kondo-like physics, spin-valve effects and induced superconductivity. We are also looking at Raman scattering from single carbon nanotubes.

   
   

3. Spintronics with GaMnAs. We combine growth at our GaAlAs MBE system with growth of GaMnAs in a MBE system at MAX LAB in Lund. We study the single crystal GaMnAs films in high magnetic fields and at low temperatures. We also look at vertical tunnel currents between the GaMnAs and GaAs and observe the circular polarized light from the electrically injected spinpolarized electrons.

Publications 2002

• "On the two-dimensional metallic state in silicon-on-insulator structures", G. Brunthaler, A. Prinz, G. Pillwein, P.E. Lindelof, and J. Ahopelto, Phys. Rev. B (2002).

• "Electron spin in single wall carbon nanotubes", P.E. Lindelof, J. Borggreen, A. Jensen, J. Nygård, and P.R. Poulsen, Invited paper for the 2001 Nobelsymposium, Göteborg, Physica Scripta TIE, in press (2002).

• "Direct capacitive coupling of Josephson oscillations to a quantum point contact", S.E. Andresen, A. Kristensen, and P.E. Lindelof, Invited paper for the Proceedings of the MS+S 2002 Conference, Tokyo, in press (2002).

• "Decoherence in Aharonov-Bohm rings", A.E. Hansen, A. Kristensen, S. Pedersen, C.B. Sørensen, and P.E. Lindelof, Physica E (2002).

• "Low temperature annealings of thin (Ga,Mn)As layers", R. Mathieu, B.S. Sørensen, J. Sadowski, J. Kanski, P. Svedlindh, and P.E. Lindelof, Submitted to Appl.Phys.Lett. (2002)

• "Magnetic anisotropy of Tunneling in GaMnAs based structures", S.E. Andresen, J. Sadowski, B.S. Sørensen, and P.E. Lindelof, Proceedings of the International Conference on the Physics of Semiconductors, Edinburg (2002).

• "Screening behavior of the two-dimensional metallic state in silicon-on-insulator structures", G. Pillwein, A. Prinz, G. Brunthaler, P.E. Lindelof, and J. Ahopelto, Proceedings of the International Conference on the Physics of Semiconductors, Edinburg (2002).

• "Dependence of Curie temperature on the thickness of epitaxial GaMnAs film", B.S. Sørensen, J. Sadowski, S.E. Andresen, and P.E. Lindelof, Phys. Rev. B (2002).

• "Quantum ratchets and quantum heat pumps", H. Linke, T.E. Humphrey, P.E. Lindelof, A. Löfgren, R. Newbury, P. Omling, A.O. Sushkov, R.P. Taylor, and H. Xu, Appl.Phys. A 75, 237 (2002).

• "Ferromagnetic GaMnAs Thinfilms", B.S. Sørensen, J. Sadowski, S.E. Andresen, P.E. Lindelof, R. Mathieu, P. Svedlindh, and J. Kanski, Proceedings of the International Conference on the Physics of Semiconductors, Edinburg (2002).