Christoph Gadermaier Department of Complex Matter Jožef Štefan Insitute Ljubljana, Slovenia

1. Systematic electron-phonon interaction strength measurements in high-temperature superconductors with femtosecond spectroscopy ChristophGadermaier Department of Complex Matter JožefŠtefanInsitute Ljubljana, Slovenia

2. Conventional superconductivity Electron-phonon interaction BCS: Isotope effect: Image courtesy of B. Valenzuela What is the role of EPI in high-Tc?

3. Determine electron phonon interaction from electron energy relaxation Image courtesy of G. Cerullo

4. The two-temperature model P.B. Allen, Phys. Rev. Lett. 59, 1460 (1987).

5. Validity of the TTM P.B. Allen, Phys. Rev. Lett. 59, 1460 (1987):

6. The non-equilibrium model V.V Kabanov and A. S. Alexandrov, Phys. Rev. B. 78, 174514 (2008).

7. e-e thermalisation is not faster than e-ph energy relaxation C. Gadermaier et al., Phys. Rev. Lett.105, 257001 (2010). Metal data from S. D. Brorson et al., Phys. Rev. Lett. 64, 2172 (1990).

8. Electron distribution during relaxation in Bi2Sr2CaCu2O8+d L. Perfetti et al., Phys. Rev. Lett. 99, 197001 (2007).

9. Compare predictions of TTM and NEM TTM NEM all fluences low fluence high fluence Te undefined

10. Temperature dependent relaxation time T. Mertelj et al., Phys. Rev. B 81, 224504 (2010). We need to measure well above the pseudogap temperature

11. Intensity independent dynamics in La1.85Sr0.15CuO4 400K < “Te” < 800 K C. Gadermaier et al., Phys. Rev. Lett.105, 257001 (2010).

12. Arguments for the non-equilibrium model • textbook knowledge • comparison of measured e-ph relaxation and estimated e-e thermalisation times • time-dependent electron distribution from ARPES • intensity independent dynamics

13. Determination of EPI strength in La1.85Sr0.15CuO4 C. Gadermaier et al., Phys. Rev. Lett.105, 257001 (2010).

14. Determination of EPI strength in YBa2Cu3O6.5 C. Gadermaier et al., Phys. Rev. Lett.105, 257001 (2010).

15. Unpublished material removed. Please contact christoph.gadermaier@ijs.si The role of e-ph interaction in high-Tc

16. Electron correlation T. Nakano et al., J. Phys. Soc. Jap. 67, 2622 (1998). J.-H. Chu, Phys. Rev. B. 79, 014506 (2009).

17. Collaborative electron-electron and electron-phonon Unpublished material removed. Please contact christoph.gadermaier@ijs.si

18. Bipolarons A. S. Alexandrov, Phys. Rev. B.38, 925 (1988). Basic theory derived already in A. S. Alexandrov, Zh. Fi. Khim. 57, 273 (1983) before the discovery of high Tc

19. Stripes and other textures T. Mertelj, V.V. Kabanov, and D. Mihailovic, Phys. Rev. Lett. 94, 147003 (2005).

20. electron-phonon interaction is determined from electron energy relaxation • electron energy relaxation is described by the non- equilibrium model, qualitatively even for non-Fermi liquids → TL/te-ph is a good measure of electron-phonon interaction • almost universal dependence of Tc of optimally doped compounds on TL/te-ph, sharp maximum at 5 K/fs→ high Tc is a collaborative effect of electron-phonon interaction and electron correlation Conclusion

21. Primož Kušar, Viktor Kabanov, Tomaž Mertelj, Ljupka Stojchevska, Yasunori Toda, Dragan Mihailović • Sasha Alexandrov • Cristian Manzoni, Daniele Brida, Dario Polli, Giulio Cerullo • grazas pola súa atención Acknowledgements