Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session

TT 33.35: Poster

Wednesday, March 28, 2012, 15:00–19:00, Poster B

Momentum-dependend quasiparticle relaxation dynamics in Bi2212 investigated by trARPES above and below T_c — •S. Freutel¹, R. Cortés^1,2, L. Rettig^1,2, Y. Yoshida³, H. Eisaki³, M. Ligges³, M. Wolf⁴, and U. Bovensiepen^1,2 — ¹Univ. Duisburg-Essen — ²Freie Univ. Berlin — ³NIAIST, Tsukuba, Japan — ⁴Fritz-Haber-Institut d.MPG, Berlin

After more than two decades of research, the understanding of high temperature superconductivity is still one of the most challenging problems of solid state physics. Femtosecond, time- and angle-resolved photo electron spectroscopy has proven to be a powerful technique to investigate the quasiparticle dynamics after optical excitation of these materials. Recent work on the optimally doped high-T_c superconductor Bi₂Sr₂CaCu₂O_2+δ [1] studied the decay times of photoexcited quasiparticles well below the transition temperature T_c at different electron momenta along the Fermi surface. At T<T_c the relaxation times exhibit no sign of a momentum dependency which was explained by blocked electron-electron scattering channel towards the nodal region due to phase space restrictions originating from the superconducting gap. Here we report independent evidence of this explanation. Since the gap vanishes at T>T_c an onset of a momentum dependence in the relaxation time would support our earlier conclusion [1]. Analyzing Bi2212 at 100 K we find a clear decrease of the relaxation time towards the nodel line from 800fs at a Fermi Surface angle of 18^∘ to 300fs at 45^∘.
Cortés et al., Phys. Rev. Lett., 107, 097002 (2011)