https://doi.org/10.1140/epjb/e2010-10743-2
Transport studies at the Mott transition of the two-dimensional organic metal κ-(BEDT-TTF)2Cu[N(CN)2]BrxCl1-x
1
Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany
2
Hochfeld-Magnetlabor Dresden,
Forschungszentrum Dresden-Rossendorf
e., V., Germany
3
Department of Applied Physics, Tafila Technical
University, Tafila, Jordan
4
Laboratoire CIMMA, UMR 6200 CNRS-Université d'Angers, Bâtiment K, UFR Sciences, 2 Boulevard Lavoisier, 49045 Angers, France
Corresponding author: a dressel@pil.physik.uni-stuttgart.de
Received:
28
September
2010
Revised:
14
November
2010
Published online:
25
January
2011
The two-dimensional organic conductor κ-(BEDT-TTF)2Cu[N(CN)2]BrxCl1-x undergoes a transition from an insulator to a superconductor upon substituting Cl by Br. We have performed in- and out-of-plane electric-transport measurements on the alloyed series with x = 20%, 40%, 70%, 80%, 85%, and 90% as a function of temperature in order to explore the bandwidth-controlled phase transition between the Mott insulator and the Fermi-liquid. All crystals exhibit a similar semiconducting behavior of ρ(T) from room temperature down to 100 K. Below approximately 50 K, a metal-to-insulator transition is found for compounds with x < 70%. Out of this Mott insulating state, magnetic order develops below TN ≈ 25 K. The Br-rich samples cross a bad-metal regime before they become coherent metals and eventually superconducting at Tc ≈ 12 K. For these systems the resistivity at Tc ≤ T ≤ T0 reveals a ρ(T) ∝ T2 dependence associated with a strongly correlated Fermi-liquid, limited by some characteristic temperature T0. The conclusions are corroborated by data from microwave, magnetic and optical experiments.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2011