Anomalous Lattice Response at the Mott Transition in a Quasi-2D Organic Conductor

M. de Souza, A. Brühl, Ch. Strack, B. Wolf, D. Schweitzer, and M. Lang
Phys. Rev. Lett. 99, 037003 – Published 18 July 2007

Abstract

Discontinuous changes of the lattice parameters at the Mott metal-insulator transition are detected by high-resolution dilatometry on deuterated crystals of the layered organic conductor κ(BEDTTTF)2Cu[N(CN)2]Br. The uniaxial expansivities uncover a striking and unexpected anisotropy, notably a zero effect along the in-plane c axis along which the electronic interactions are relatively strong. A huge thermal expansion anomaly is observed near the end point of the first-order transition line enabling us to explore the critical behavior with very high sensitivity. The analysis yields critical fluctuations with an exponent α˜0.8±0.15 at odds with the novel criticality recently proposed for these materials [Kagawa et al., Nature (London) 436, 534 (2005)]. Our data suggest an intricate role of the lattice degrees of freedom in the Mott transition for the present materials.

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  • Received 18 October 2006

DOI:https://doi.org/10.1103/PhysRevLett.99.037003

©2007 American Physical Society

Authors & Affiliations

M. de Souza1, A. Brühl1, Ch. Strack1, B. Wolf1, D. Schweitzer2, and M. Lang1

  • 1Physikalisches Institut, J. W. Goethe-Universität Frankfurt(M), FOR 412, D-60054 Frankfurt am Main, Germany
  • 23. Physikalisches Institut, Universität Stuttgart, D-70550 Stuttgart, Germany

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Vol. 99, Iss. 3 — 20 July 2007

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