Evidence for an incommensurate charge density wave instability in η-Mo4O11

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Abstract
Eta -Mo4O11 was known to be a quasi-two-dimensional metal showing two phase transitions at TC1=109K and TC2=30K. Electron diffraction and X-ray diffuse scattering studies now establish that weak satellite reflections appear below TC1 and therefore that the high-temperature transition is accomplished by a structural modulation towards an incommensurate charge density wave state characterised by the wave-vector (0,0.23,0). The magnetic susceptibility found to be strongly anisotropic below TC1, is consistent with the opening of partial gaps at the Fermi surface and with an anisotropic Landau diamagnetism related to the CDW state. De Haas-van Alphen oscillations also corroborate the existence below TC1 of small electron and hole pockets.