1. 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, Weizmann Institute of Science - Rehovot M. Feigel’man, L. D. Landau Institute for Theoretical Physics - Moscow Schegolev Memorial Conference 2009 STM on highly disordered superconducting films

2. Outline The superconductor-insulator transition The superconductor-insulator transition Spectroscopy at 50 mK in TiN films Spectroscopy at 50 mK in TiN films Spectroscopy above Tc in TiN films Spectroscopy above Tc in TiN films Spectroscopya-InO films Spectroscopy below and above Tc in a-InO films Conclusions Conclusions Schegolev Memorial Conference 2009

3. 1/T [K] Titanium nitride thin films d = 5 nm T. I. Baturina, A Yu Mironov, V. M. Vinokur, M. R. Baklanov and C. Strunk PRL 99, 257003 (2007) Continuous decrease of Tc with increasing disorder Activated behavior : superconductivity related ? I1 : T 0 = 0.25 K I2 : T 0 = 0.38 K I3 : T 0 = 0.61 K SIT

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

5. V. F. Gantmakher et al., JETP 82, 951 (1996) D. Shahar and Z. Ovadyahu, Phys. Rev. B 46, 10917, (1992) Indium oxide thin films d = 20 nm - 200 nm SIT Activation energy T 0 converges towards T c

6. Outline The superconductor-insulator transition The superconductor-insulator transition Spectroscopy at 50 mK in TiN films Spectroscopy at 50 mK in TiN films Spectroscopy above Tc in TiN films Spectroscopy above Tc in TiN films Spectroscopya-InO films Spectroscopy below and above Tc in a-InO films Conclusions Conclusions Schegolev Memorial Conference 2009

7. T c [K]Δ/T c 4.71.8 1.32.3 12.6 0.454 Increasing disorder Sacépé et al. PRL 101, 157006 (2008) Tunneling spectroscopy at 50 mK in TiN Transport and tunneling spectroscopy

8. T c [K]Δ/T c 4.71.8 1.32.3 12.6 0.454 λ λ Increasing disorder A. Ghosal, M. Randeria, N. Trivedi, Phys. Rev. Lett. 81, 3940, (1998) - Phys. Rev. B 65, 014501 (2001) Tunneling spectroscopy at 50 mK in TiN

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

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

11. TiN 1 (T c = 1.3 K) A. Ghosal, M. Randeria, N. Trivedi, Phys. Rev. Lett. 81, 3940, (1998) Δ(r) T c [K]Δ/T c Var. [%] 4.71.8--- 1.32.312 12.620 0.45450 11 B. Sacépé, et al. Phys. Rev. Lett. 101, 157006, (2008) Tunneling spectroscopy at 50 mK in TiN Inhomogeneous superconducting state

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

13. Outline The superconductor-insulator transition The superconductor-insulator transition Spectroscopy at 50 mK in TiN films Spectroscopy at 50 mK in TiN films Spectroscopy above Tc in TiN films Spectroscopy above Tc in TiN films Spectroscopya-InO films Spectroscopy below and above Tc in a-InO films Conclusions Conclusions Schegolev Memorial Conference 2009

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

15. Tunneling spectroscopy above Tc in TiN

17. T c [K] 1.3 1 0.45 One parameter fit : T c Tunneling spectroscopy above Tc in TiN

18. Superconducting fluctuations correction to the DOS A. Varlamov and V. Dorin, Sov. Phys. JETP 57, 1089, (1983) Slopes increase with G i ~ R □ Valid up to ε > 1 R □ [kΩ] T c (R □ ) [K] T c (DOS) [K] 3.51.31.27 4.31.00.98 7.40.450.45 Validity : Tunneling spectroscopy above Tc in TiN

19. Superconducting fluctuations correction to the DOS A. Varlamov and V. Dorin, Sov. Phys. JETP 57, 1089, (1983) Striking sensitivity to Tc R □ [kΩ] T c (R □ ) [K] T c (DOS) [K] 3.51.31.27 4.31.00.98 7.40.450.45 Tunneling spectroscopy above Tc in TiN

20. Outline The superconductor-insulator transition The superconductor-insulator transition Spectroscopy at 50 mK in TiN films Spectroscopy at 50 mK in TiN films Spectroscopy above Tc in TiN films Spectroscopy above Tc in TiN films Spectroscopya-InO films Spectroscopy below and above Tc in a-InO films Conclusions Conclusions Schegolev Memorial Conference 2009

21. Strong inhomogeneities : Spectra measured at different locations Tunneling spectroscopy in InO Indium oxide thin films d = 15 -35 nm

22. Strong inhomogeneities : Spectra measured at different locations Tunneling spectroscopy in InO Indium oxide thin films d = 15 -35 nm

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

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

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