Density-wave instability in α−(BEDT-TTF)2KHg(SCN)4 studied by x-ray diffuse scattering and by first-principles calculations

Pascale Foury-Leylekian, Jean-Paul Pouget, Young-Joo Lee, Risto M. Nieminen, Pablo Ordejon, Enric Canadell

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23 Citations (Scopus)
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Abstract

α−(BEDT-TTF)2KHg(SCN)4 develops a density wave ground state below 8 K whose origin is still debated. Here we report a combined x-ray diffuse scattering and first-principles density functional theory study supporting the charge density wave (CDW) scenario. In particular, we observe a triply incommensurate anharmonic lattice modulation with intralayer wave vector components which coincide within experimental errors to the maximum of the calculated Lindhard response function. A detailed study of the structural aspects of the modulation shows that the CDW instability in α−(BEDT-TTF)2KHg(SCN)4 is considerably more involved than those following a standard Peierls mechanism. We thus propose a microscopic mechanism where the CDW instability of the BEDT-TTF layer is triggered by the anion sublattice. Our mechanism also emphasizes the key role of the coupling of the BEDT-TTF and anion layers via the hydrogen bond network to set the global modulation.
Original languageEnglish
Article number134116
Pages (from-to)1-14
JournalPhysical Review B
Volume82
Issue number13
DOIs
Publication statusPublished - 2010
MoE publication typeA1 Journal article-refereed

Keywords

  • density-wave
  • first principles
  • x-ray scattering

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