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

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.

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density-wave, first principles, x-ray scattering

DOI

10.1103/PhysRevB.82.134116

Citation

Foury-Leylekian, P, Pouget, J-P, Lee, Y-J, Nieminen, R M, Ordejon, P & Canadell, E 2010, 'Density-wave instability in α−(BEDT-TTF)2KHg(SCN)4 studied by x-ray diffuse scattering and by first-principles calculations', Physical Review B, vol. 82, no. 13, 134116, pp. 1-14. https://doi.org/10.1103/PhysRevB.82.134116

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https://urn.fi/URN:NBN:fi:aalto-201805222726

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[article-cris] Perustieteiden korkeakoulu / SCI

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

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