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Impurity-Mediated Early Condensation of a Charge Density Wave in an Atomic Wire Array
Yeom, Han Woong,Oh, Deok Mahn,Wippermann, Stefan,Schmidt, Wolf Gero American Chemical Society 2016 ACS NANO Vol.10 No.1
<P>We directly show how impurity atoms induce the condensation of a representative electronic phase, the charge density wave (CDW) phase, in atomic scale with scanning tunneling microscopy. Oxygen impurity atoms on the self-assembled metallic atomic wire array on a silicon crystal condense the CDW locally above the pristine transition temperature. More interestingly, the CDW along the wires is induced not by a single atomic impurity but by the cooperation of multiple impurities. First principles calculations disclose the mechanism of the cooperation as the coherent superposition of the local lattice strain induced by impurities, stressing the coupled electronic and lattice degrees of freedom for the CDW. This opens the possibility of the strain engineering over electronic phases of atomic-scale systems.</P>
Dynamical Metal to Charge-Density-Wave Junctions in an Atomic Wire Array
Song, Sun Kyu,Samad, Abdus,Wippermann, Stefan,Yeom, Han Woong American Chemical Society 2019 NANO LETTERS Vol.19 No.8
<P>We investigated the atomic scale electronic phase separation emerging from a quasi-1D charge-density-wave (CDW) state of the In atomic wire array on a Si(111) surface. Spatial variations of the CDW gap and amplitude are quantified for various interfaces of metallic and insulating CDW domains by scanning tunneling microscopy and spectroscopy (STS). The strong anisotropy in the metal-insulator junctions is revealed with an order of magnitude difference in the interwire and intrawire junction lengths of 0.4 and 7 nm, respectively. The intrawire junction length is reduced dramatically by an atomic scale impurity, indicating the tunability of the metal-insulator junction in an atomic scale. Density functional theory calculations disclose the dynamical nature of the intrawire junction formation and tunability.</P> [FIG OMISSION]</BR>