Phase-transition anomalies in the lattice response around 40 K in superconducting κ-(BEDT-TTF)2X

M. Lang, J. Müller, F. Steglich, J. A. Schlueter, A. M. Kini, T. Sasaki

Research output: Contribution to journalConference articlepeer-review

9 Citations (Scopus)


High-resolution measurements of the coefficient of thermal expansion, α(T), on the superconductors κ-(BEDT-TTF)2X with X = Cu[N(CN)2]Br and Cu(NCS)2 reveal distinct anomalies at T* around 40 K - the same temperature where the opening of a pseudo-gap has been inferred from anomalies in various thermal and magnetic properties. Judging from the shape of the α anomalies, we tend to assign these features to broadened second-order phase transitions. Employing a thermodynamic analysis, the signs of the uniaxial-pressure coefficients of T* can be determined and are found to be strictly anticorrelated to those of Tc. We propose that T* marks a density-wave (DW) instability involving only the small, quasi-1D portions of the Fermi surface (FS) as opposed to a pseudo-gap on the whole FS. Our scenario implies that the DW and superconductivity form on disjunct parts of the FS and compete for stability.

Original languageEnglish
Pages (from-to)107-110
Number of pages4
JournalSynthetic Metals
Publication statusPublished - 2003 Mar 13
EventISCOM 2001 - Rusutsu, Hokkaido, Japan
Duration: 2001 Sept 102001 Sept 14


  • BEDT-TTF salts
  • Lattice properties
  • Organic superconductors


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