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Vortex Pinning and Sliding in Superconductors

Vortex Pinning and Sliding in Superconductors. Charles Simon, laboratoire CRISMAT, CNRS. Laboratoire CRISMAT A. Pautrat C. Goupil Ecole Normale Supérieure Paris P. Mathieu LEMA Tours A. Ruyter L. Ammor Laboratoire Léon Brillouin Brûlet Institut Laue Langevin C. Dewhurst.

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Vortex Pinning and Sliding in Superconductors

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  1. Vortex Pinning and Sliding in Superconductors Charles Simon, laboratoire CRISMAT, CNRS

  2. Laboratoire CRISMAT • A. Pautrat • C. Goupil • Ecole Normale Supérieure Paris • P. Mathieu • LEMA Tours • A. Ruyter • L. Ammor • Laboratoire Léon Brillouin • Brûlet • Institut Laue Langevin • C. Dewhurst

  3. IIntroduction to vortex pinning and dynamics II A neutron diffraction study in low Tc materials III The peak effect in NbSe2 IV The surface pinning in Bi-2212 V Conclusions

  4. Vortex dynamics FL Vff 3 V 2 (B) I c 1 Nb-Ta 0.3 T 4.2 K 0 20 0 5 10 15 V (mV) 0.2 T 0.1 T B I I (A) E=B. Vff V= Rff(B,T) (I-Ic(B,T))

  5. Typical disordered elastic system with pinning and sliding with the possibility to vary the intensity of the pinning by changing the magnetic field. • But from the beginning: problems (shape of the IV, …) • Here : Low temperature physics • Neutron scattering, very difficult but quite simple to interpret (10 years)

  6. B Bc2 Normal phase Bc1 Meissner T Neutron scattering Niobium Nb-Ta Bi-2212

  7. T. Giamarchi and P. Le Doussal, Phys. Rev. Lett. 72, 1530 (1994). and Phys. Rev. B 52, 1242 (1995). Cubitt, R. et al. Nature 365, 407-411 (1993). B(G)

  8. T. Klein et al., Nature 413, (2001) 404

  9. Neutrons with current Nb-Ta singlecrystal P. Thorel and al., J. Phys. (Paris) 34, 447 (1973). A. Pautrat, Phys. Rev. Lett. 90,   087002   (2003).

  10. Neutrons with current Nb-Ta singlecrystal

  11. neutrons w B Ic/2 Ic/2 Ibulk=0 Ibulk=(I-Ic) Ic/2 Ic/2 How flows the current? curl B = m0J tan (Dw) = by / B = m0Jxe / B A. Pautrat, et al. Phys. Rev. Lett. 90, 087002 (2003)

  12. V(mV) Ic I (A) surface pinning (Pb-In) Surface treatments Ic (Amp)

  13. q cr n Boundary conditions ic lvl (moe/B)1/2 ao P. Mathieu et Y. Simon, Europhys Lett 5, 1988 ~ 0-100 A/cm B Why surface pinning? Normal rough surface 1000 Å ic (A/m) = e . sin qcr MS length

  14. k = 1 e / HC2 B / BC2 Quantitative prediction Numerical solution of Ginzburg equations by Guilpin and Simon Nb film • Quantitative analysis of the critical current due to vortex pinning by surface corrugation • Pautrat, J. Scola, C. Goupil, Ch. Simon, C. Villard, B. Domengès, Y. Simon, • Phys. Rev. B 69, 224504 (2004)

  15. 0 A Rough surface Smooth surface 20 A V=Rff (I-Ic) V (mV) V (mV) V(mV) w (deg) Dw (deg) Dw (deg) I(A) I (Amp) I (Amp) What happens at high current?

  16. V (mV) Dw (deg) Ic2 Ic2 Ic1 Ic1 < I < Ic2 Inhomogeneous critical current

  17. The peak effect in NbSe2 Metastable states of a flux-line lattice studied by transport and small-angle neutron A. Pautrat, J. Scola, Ch. Simon, P. Mathieu, A. Brûlet, C. Goupil, M. J. Higgins, Phys. Rev. B 71, 064517 (2005)

  18. NbSe2

  19. Iron doped NbSe2

  20. T. Klein et al., Nature 413, (2001) 404

  21. Bi-2212 Transport in the peak effect

  22. Bi-2212 Persistence of an ordered flux line lattice above the second peak in Bi2Sr2CaCu2O8+δ A. Pautrat, Ch. Simon, C. Goupil, P. Mathieu, A. Brûlet, C. D. Dewhurst, and A. I. Rykov Phys. Rev. B 75, 224512 (2007)

  23. Bi-2212 with columnar defects Microbridge 50mm 20 mm BF=1T 5K 0.4T Surface vortex depinning in an irradiated single crystal microbridge of Bi2Sr2CaCu2O8+δ : Crossover from individual to collective bulk pinning A. Ruyter, D. Plessis, Ch. Simon, A. Wahl, and L. Ammor Phys. Rev. B 77, 212507 (2008)

  24. Do columnar defects product bulk pinning? No, there is no bulk currents

  25. Reversible magnetization A. Wahl et al., Physica C 250 163(1995) R. J. Drost et al, PRB 58 R615 (1998)

  26. Conclusions • Very powerful technique • Surface currents • Peak effect = metastable states • What is the limit of this stability? • Noise measurements, ac response, Hall effects…

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