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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]Br_xCl_1−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.