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

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© 2010 American Physical Society (APS). This is the accepted version of the following article: Foury-Leylekian, Pascale & Pouget, Jean-Paul & Lee, Young-Joo & Nieminen, Risto M. & Ordejón, Pablo & Canadell, Enric. 2010. Density-wave instability in alpha-(BEDT-TTF)2KHg(SCN)4 studied by x-ray diffuse scattering and by first-principles calculations. Physical Review B. Volume 82, Issue 13. 134116/1-14. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.82.134116, which has been published in final form at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.82.134116.

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Journal Title

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Volume Title

School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä

Date

2010

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Mcode

Degree programme

Language

en

Pages

134116/1-14

Series

Physical Review B, Volume 82, Issue 13

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.

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Keywords

density waves, instability

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Citation

Foury-Leylekian, Pascale & Pouget, Jean-Paul & Lee, Young-Joo & Nieminen, Risto M. & Ordejón, Pablo & Canadell, Enric. 2010. Density-wave instability in alpha-(BEDT-TTF)2KHg(SCN)4 studied by x-ray diffuse scattering and by first-principles calculations. Physical Review B. Volume 82, Issue 13. 134116/1-14. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.82.134116.