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B. Sacépé, T. Dubouchet, C. Chapelier, M. Sanquer, CEA - Grenoble

Schegolev Memorial Conference 2009. STM on highly disordered superconducting films. B. Sacépé, T. Dubouchet, C. Chapelier, M. Sanquer, CEA - Grenoble T. Baturina, Institute of semiconductor Physics - Novosibirsk V. Vinokur, Material Science Division, Argonne National Laboratory - Argonne

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B. Sacépé, T. Dubouchet, C. Chapelier, M. Sanquer, CEA - Grenoble

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  1. Schegolev Memorial Conference2009 STM on highly disordered superconducting films B. Sacépé, T. Dubouchet, C. Chapelier, M. Sanquer, CEA - Grenoble T. Baturina, Institute of semiconductor Physics - Novosibirsk V. Vinokur, Material Science Division, Argonne National Laboratory - Argonne M. Baklanov, A Satta, IMEC - Leuven M. Ovadia, D. Shahar,WeizmannInstitute of Science - Rehovot M. Feigel’man, L. D. Landau Institute for Theoretical Physics - Moscow

  2. Schegolev Memorial Conference2009 Outline • The superconductor-insulator transition • Spectroscopy at 50 mK in TiN films • Spectroscopy above Tc in TiN films • Spectroscopy below and above Tc in a-InO films • Conclusions

  3. SIT 1/T [K] Titaniumnitridethin filmsd = 5 nm Continuous decrease of Tc with increasing disorder I1 : T0 = 0.25 K I2 : T0 = 0.38 K I3 : T0 = 0.61 K Activated behavior : superconductivity related ? T. I. Baturina, A Yu Mironov, V. M. Vinokur, M. R. Baklanov and C. Strunk PRL 99, 257003 (2007)

  4. SIT Magneto-resistance peak Magneto-resistance peak : superconductivity related ? T. I. Baturina, C. Strunk, M. R. Baklanov, and A. Satta PRL 98, 127003 (2007)

  5. SIT Indium oxide thin filmsd = 20 nm - 200 nm V.F.Gantmakher et al., JETP 82, 951 (1996) Activationenergy T0 converges towards Tc D. Shahar and Z. Ovadyahu, Phys. Rev. B 46, 10917, (1992)

  6. Schegolev Memorial Conference2009 Outline • The superconductor-insulator transition • Spectroscopy at 50 mK in TiN films • Spectroscopy above Tc in TiN films • Spectroscopy below and above Tc in a-InO films • Conclusions

  7. Tunneling spectroscopy at 50 mK in TiN Transport and tunneling spectroscopy Sacépé et al. PRL 101, 157006 (2008) Increasingdisorder

  8. Tunneling spectroscopy at 50 mK in TiN λ λ Increasingdisorder A. Ghosal, M. Randeria, N. Trivedi,Phys. Rev. Lett. 81, 3940, (1998) - Phys. Rev. B 65, 014501 (2001)

  9. Tunneling spectroscopy at 50 mK in TiN λ Tunneling spectroscopy at 50 mK in TiN Inhomogeneous superconducting state M. Ma and P.A. Lee, Phys. Rev. B 32, 5658, (1985) A. Ghosal, M. Randeria, N. Trivedi, Phys. Rev. Lett. 81, 3940, (1998) Phys. Rev. B 65, 014501 (2001)

  10. Tunneling spectroscopy at 50 mK in TiN Coulomb suppression and mesoscopic fluctuations of Tc A. M. Finkelstein, Pis’sma Zh. Eksp. Theor. Fiz., 45, 46 (1987) M. A. Skvortsov and M. V. Feigel’man,Phys. Rev. Lett. 95, 057002, (2005)

  11. Tunneling spectroscopy at 50 mK in TiN Inhomogeneous superconducting state TiN 1 (Tc = 1.3 K) Δ(r) A. Ghosal, M. Randeria, N. Trivedi, Phys. Rev. Lett. 81, 3940, (1998) B. Sacépé, et al.Phys. Rev. Lett. 101, 157006, (2008) 11

  12. Tunneling spectroscopy at 50 mK in TiN Tunneling spectroscopy at Low temperatureSummary Activated behavior A. M. Finkelstein, Pis’sma Zh. Eksp. Theor. Fiz., 45, 46 (1987)

  13. Schegolev Memorial Conference2009 Outline • The superconductor-insulator transition • Spectroscopy at 50 mK in TiN films • Spectroscopy above Tc in TiN films • Spectroscopy below and above Tc in a-InO films • Conclusions

  14. Tunneling spectroscopy above Tc in TiN Temperature evolution of the tunneling conductance TiN 2 – Tc = 1 K (close to the SIT) TiN bulk – Tc = 4.7 K (far from the SIT) Superconducting fluctuations W. Escoffier, et al.,Phys. Rev. Lett. 93, 217005, (2004) 14

  15. Tunneling spectroscopy above Tc in TiN

  16. Tunneling spectroscopy above Tc in TiN

  17. Tunneling spectroscopy above Tc in TiN One parameter fit : Tc

  18. Tunneling spectroscopy above Tc in TiN Validity : Superconducting fluctuations correction to the DOS A. Varlamov and V. Dorin, Sov. Phys. JETP 57, 1089, (1983) Slopes increase with Gi ~ R□ Valid up to ε> 1

  19. Tunneling spectroscopy above Tc in TiN Superconducting fluctuations correction to the DOS A. Varlamov and V. Dorin, Sov. Phys. JETP 57, 1089, (1983) Striking sensitivity to Tc

  20. Schegolev Memorial Conference2009 Outline • The superconductor-insulator transition • Spectroscopy at 50 mK in TiN films • Spectroscopy above Tc in TiN films • Spectroscopy below and above Tc in a-InO films • Conclusions

  21. Tunneling spectroscopy in InO Indium oxidethin filmsd = 15 -35 nm Spectra measured at different locations Strong inhomogeneities :

  22. Tunneling spectroscopy in InO Indium oxidethin filmsd = 15 -35 nm Spectra measured at different locations Strong inhomogeneities :

  23. Tunneling spectroscopy at 50 mK in TiN λ λ Inhomogeneous superconducting state M. Ma and P.A. Lee, Phys. Rev. B 32, 5658, (1985) A. Ghosal, M. Randeria, N. Trivedi, Phys. Rev. Lett. 81, 3940, (1998) Phys. Rev. B 65, 014501 (2001)

  24. Tunneling spectroscopy in InO λ Superconducting gap « Insulating » gap A. Ghosal, M. Randeria, N. Trivedi, Phys. Rev. Lett. 81, 3940, (1998) Phys. Rev. B 65, 014501 (2001)

  25. Tunneling spectroscopy in InO Proliferation of spectra without coherence peaks when approaching the insulating state

  26. Tunneling spectroscopy in InO Pseudogaps without coherence peaks : signature of localized Cooper pairs see M. Feigel’man talk (this session) T(peak) = Tc for any local gap amplitude

  27. Conclusions Superconducting inhomogeneous state with non-zero gap at the SIT at T=0 Pseudogap state above Tc described by the superconducting fluctuations Localization of Cooper pairs

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