Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 34: Correlated Electrons: Metal-Insulator Transition 2
TT 34.18: Vortrag
Donnerstag, 28. Februar 2008, 18:45–19:00, H 2053
Dynamics of correlated charge carriers in the close proximity to the Mott-Hubbard transition — •Michael Dumm1, D. Faltermeier1, S. Yasin1, N. Drichko1, M. Dressel1, and J. Merino2 — 11. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart — 2Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Madrid 28049, Spain
We explored the dynamics of correlated charge carriers in close proximity to the Mott-Hubbard transition experimentally and theoretically in the quasi two-dimensional organic conductor κ-(BEDT-TTF)2Cu[N(CN)2]BrxCl1−x (x = 0.73 and 0.85). In the dc and optical conductivity data, we observe typical signatures of Fermi liquid behavior below the characteristic temperature T∗ ≈ 30 K and frequency ν∗≈ 400 cm−1: a T2 and ν2 dependence in resistivity and scattering rate, respectively and a substantial enhancement of the effective mass of the correlated carriers once we approach the metal-to-insulator transition by increasing U/t, i. e. by decreasing the Br content. The experimental results obtained by infrared spectroscopy agree well with DMFT calculations of a Hubbard model on a frustrated square lattice. Both, temperature and frequency dependence of optical conductivity and effective charge carrier number are successfully described by the theoretical model. If the temperature is increased above T∗, the Drude peak observed in the optical data at T< T∗ and ν < ν∗ vanishes and the optical spectral weight of the correlated carriers decreases indicating a gradual destruction of the quasiparticles.