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[Fizinfo] BME Fizika Tanszék szemináriuma

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  • From: Halbritter András <halbritt AT>
  • To: fizinfo AT
  • Subject: [Fizinfo] BME Fizika Tanszék szemináriuma
  • Date: Wed, 27 Jan 2010 08:54:42 -0000
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  • List-id: ELFT HÍRADÓ <>

a BME Fizikai Intezet, Fizika Tanszek

Jan Martinek
Institute of Molecular Physics,
Polish Academy of Sciences,
60-179 Poznan, Poland

"Kondo effect in the presence of ferromagnetism
in quantum dots coupled to ferromagnetic leads"

The manipulation of magnetization and spin is one of the fundamental processes in magneto-electronics and spintronics, providing the possibility of writing information in a magnetic memory, and also because of the possibility of classical or quantum computation using spin. In most situations, this is realized by means of an externally applied nonlocal magnetic field, which is usually difficult to introduce into an integrated circuit. We propose to control the amplitude and sign of the spin-splitting of a quantum dot induced by the presence of ferromagnetic leads, using a gate voltage without further assistance of a magnetic field [1-3]. We study the effect of a gate voltage on the spin splitting of an electronic level in a quantum dot attached to ferromagnetic in the Kondo regime using a generalized numerical renormalization group technique [2,3]. We extended Wilson’s numerical renormalization group method, extended to handle leads with a spin asymmetric density of states, to identify the effects of (i) a finite spin polarization in the leads at the Fermi surface, (ii) a Stoner splitting in the bands governed by the band edges, and (iii) an arbitrary shape of the lead density of states. We give an analytical description of our numerical results using perturbative scaling analysis and explain how the effect arises due to spin-dependent charge fluctuations.
A conceivable realization of proposed system might be carbon nanotubes or other molecular systems in contact to ferromagnetic leads (ferromagnetic single-molecule transistor) [4]. New experimental results for a single carbon nanotube attached to nickel electrodes confirm the theoretical predictions [5].

1. J. Martinek, Y. Utsumi, H. Imamura, J. Barnas, S. Maekawa, J. König, and G. Schön, Phys. Rev. Lett. 91, 127203 (2003);
2. J. Martinek, M. Sindel, L. Borda, R. Bulla, J. König, G. Schön, S. Maekawa, and J. von Delft, Phys. Rev. Lett. 91, 247202 (2003); Phys. Rev. B 72, 121302 (2005).
3. M. Sindel, L. Borda, J. Martinek, R. Bulla, J. König, G. Schön, S. Maekawa, and J. von Delft, Phys. Rev. B 76, 045321 (2007).
4. A. N. Pasupathy, R. C. Bialczak, J. Martinek, J. E. Grose, L. A. K. Donev, P. L. McEuen, and D. C. Ralph, Science 306, 86 (2004).
5. J. R. Hauptmann, J. Paaske, and P.E. Lindelof, Nature Physics, (2008).

Helye: BME Fizikai Intezet, Fizika Tanszek
Budafoki ut 8.
F-epulet, III. lepcsohaz, 2. em. 13. előadóterem

Ideje: 2010. februar 2. kedd, 10:15.

Minden erdeklodot szivesen latunk.

Halbritter András

Budapest University of Technology and Economics
Department of Physics
1111 Budapest Budafoki út 8.
Tel: +36 1 4631650
Fax: +36 1 4634180

  • [Fizinfo] BME Fizika Tanszék szemináriuma, Halbritter András, 01/27/2010

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