Order and Low Dimensionality in the Organic Superconductor (BEDT-TTF)2Cu(NCS)2 Revealed by STM

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Science  15 May 1992:
Vol. 256, Issue 5059, pp. 1012-1014
DOI: 10.1126/science.256.5059.1012


Single-crystal samples of [(BEDT-TTF)2]+[Cu(NCS)2]-were synthesized and studied with a scanning tunneling microscope (STM). Real-space images of the anion and cation surfaces with molecular resolution were obtained. The images show no evidence of structural disorder or stacking faults previously suggested. The presence of an additional modulation commensurate with the lattice provides evidence of a lattice distortion. The cause of this modulation is unknown. The presence of a charge density wave in the material would have implications on the dimensionality of the material that may explain the peculiar temperature dependence of the electrical conductivity. This interpretation is consistent with the calculated Fermi surface, which allows nesting of the wave vector.