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Spin thermopower in the overscreened Kondo model

NanoCTM final network meeting and workshop Poznań, 23-27 September 2013. Spin thermopower in the overscreened Kondo model. Tomaž Rejec, Rok Žitko, Jernej Mravlje and Anton Ramšak Department of Physics, University of Ljubljana Jožef Stefan Institute, Ljubljana. Outline.

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Spin thermopower in the overscreened Kondo model

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  1. NanoCTM final network meeting and workshop Poznań, 23-27 September 2013 Spin thermopower in the overscreened Kondo model Tomaž Rejec, Rok Žitko, Jernej Mravlje and Anton Ramšak Department of Physics, University of Ljubljana Jožef Stefan Institute, Ljubljana

  2. Outline • Spin-Seebeck coefficient • Kondo models (fully screened, underscreened, overscreened) • NRG results

  3. Spin-Seebeck coefficient TL=TR L V=0 R

  4. Spin-Seebeck coefficient TL=TR L V≠0 R

  5. Spin-Seebeck coefficient TL=TR L V≠0 R

  6. Spin-Seebeck coefficient TL>TR L V=0 R

  7. Spin-Seebeck coefficient TL>TR L V=0 R

  8. Spin-Seebeck coefficient TL>TR L ed≠0 V=0 R

  9. Spin-Seebeck coefficient TL>TR L ed≠0 V≠0 R Seebeck coefficient

  10. Spin-Seebeck coefficient TL>TR L B≠0 V=0 R

  11. Spin-Seebeck coefficient TL>TR L B≠0 V=0 R Spin current!

  12. Spin-Seebeck coefficient TL>TR L B≠0 Vs≠0 R Spin-Seebeck coefficient Spin voltage:

  13. Spin-Seebeck coefficient For small DT, Vs: Non-interacting QD: B>G B=G B<G

  14. Kondo models NFL: J1=J2 : overscreened Kondo effect

  15. Kondo models

  16. Kondo models S=1/2; i=1 : fully screened Kondo model S=1/2; i=1,2 : overscreened Kondo model S=1; i=1 : underscreened Kondo model

  17. Results – fully screened Kondo model B=TK B>G B=G B<G

  18. Results – overscreened Kondo model NFL FL

  19. Results – underscreened Kondo model

  20. Summary • Measuring the spin thermopower at low magentic fields would provide a sensitive test for distinguishing between fully screened, underscreened and overscreened Kondo behaviour • Possible applications: generation of spin current for spintronics applications, sensitive measurement of low magnetic fields

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