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Christoph Gadermaier Department of Complex Matter Jožef Štefan Insitute Ljubljana, Slovenia - PowerPoint PPT Presentation


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Systematic electron-phonon interaction strength measurements in high-temperature superconductors with femtosecond spectroscopy. Christoph Gadermaier Department of Complex Matter Jožef Štefan Insitute Ljubljana, Slovenia. Conventional superconductivity Electron-phonon interaction. BCS:.

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Systematic electron-phonon interaction strength measurements in high-temperature superconductors with femtosecond spectroscopy

ChristophGadermaier

Department of Complex Matter

JožefŠtefanInsitute

Ljubljana, Slovenia


Conventional superconductivity in high-temperature superconductors with femtosecond spectroscopy

Electron-phonon interaction

BCS:

Isotope effect:

Image courtesy of B. Valenzuela

What is the role of EPI in high-Tc?


Determine electron phonon interaction from electron energy relaxation

Image courtesy of G. Cerullo


The two-temperature model relaxation

P.B. Allen, Phys. Rev. Lett. 59, 1460 (1987).


Validity of the TTM relaxation

P.B. Allen, Phys. Rev. Lett. 59, 1460 (1987):


The non-equilibrium model relaxation

V.V Kabanov and A. S. Alexandrov, Phys. Rev. B. 78, 174514 (2008).


e-e thermalisation is not faster than e-ph energy relaxation 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).


Electron distribution during relaxation in Bi relaxation2Sr2CaCu2O8+d

L. Perfetti et al., Phys. Rev. Lett. 99, 197001 (2007).


Compare predictions of TTM and NEM relaxation

TTM

NEM

all fluences

low fluence

high fluence

Te undefined


Temperature dependent relaxation time relaxation

T. Mertelj et al., Phys. Rev. B 81, 224504 (2010).

We need to measure well above the pseudogap temperature


Intensity independent dynamics in La relaxation1.85Sr0.15CuO4

400K < “Te” < 800 K

C. Gadermaier et al., Phys. Rev. Lett.105, 257001 (2010).


Arguments for the non-equilibrium model relaxation

  • textbook knowledge

  • comparison of measured e-ph relaxation and estimated e-e thermalisation times

  • time-dependent electron distribution from ARPES

  • intensity independent dynamics


C. Gadermaier et al., Phys. Rev. Lett.105, 257001 (2010).


C. Gadermaier et al., Phys. Rev. Lett.105, 257001 (2010).


Unpublished material removed. Please contact [email protected]

The role of e-ph interaction in high-Tc


Electron correlation [email protected]

T. Nakano et al., J. Phys. Soc. Jap. 67, 2622 (1998).

J.-H. Chu, Phys. Rev. B. 79, 014506 (2009).



Bipolarons [email protected]

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


Stripes and other textures [email protected]

T. Mertelj, V.V. Kabanov, and D. Mihailovic, Phys. Rev.

Lett. 94, 147003 (2005).


  • electron-phonon interaction is determined from electron [email protected] 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


Acknowledgements


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