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TT: Fachverband Tiefe Temperaturen

TT 1: Focussed Session: The Mott Transition in Model Systems

TT 1.3: Topical Talk

Montag, 23. März 2009, 11:15–11:45, HSZ 03

Carrier dynamics of two-dimensional organic charge-transfer salts close to the Mott transition — •Martin Dressel¹, Natalia Drichko¹, Michael Dumm¹, and Jaime Merino² — ¹1. Physikalisches Institut, Universität Stuttgart, Germany — ²Departamento de Física Teórica de la Materia, Universidad Autónoma de Madrid, Spain

In recent years, it became clear that electronic interactions have a severe influence on the physics of two-dimensional electron systems [1-3]. Strong Coulomb repulsion drives a transition to a Mott-insulator in a half-filled meta, while in the case of a quarter-filled conduction band charge order is observed. Optical spectroscopy is the superior method to investigate the electronic properties. Our findings on organic crystals are compared with theoretical predictions.

Organic conductors serve as model systems to study physics in two-dimensions. The Mott transition can be tuned by decreasing the temperature or by increasing the effective electronic correlations. Physical and chemical pressure are proper tools to tune the bandwidth; doping or change of the stoichiometry allow for a variation of the carrier concentration. Close to the Mott transition but still on the metallic side, quasi-particles are observed in the 1/2-filled system κ-(BEDT-TTF)₂Cu[N(CN)₂]X only at temperatures well below 100 K, with a considerable growth of the Drude-like contribution. The itinerant carriers exhibit strong renormalization effects as the metal-insulator transition is approached.

[1] M. Dressel et al., Chem. Rev. 104 5689 (2004).

[2] D. Faltermeier, et al., PRB 76, 165113 (2007).

[3] J. Merino, et al., PRL 100, 086404 (2008).