Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 7: Symposium: Atomic Wires at Surfaces I
(Invited Speakers: Franz Himpsel, Hanno Weitering, Han Woong Yeom)

O 7.4: Vortrag

Montag, 25. Februar 2008, 12:15–12:30, HE 101

Electrons Confined to Atomic Nanowires of Au on Ge(001) — •Jörg Schäfer, Christian Blumenstein, Sebastian Meyer, Marc Wisniewski, and Ralph Claessen — Physikalisches Institut, Universität Würzburg, D-97074 Würzburg

Nanowires reach their lower size limit in metal-induced chains on semiconductors. In such quasi-one-dimensional (1D) systems, the Fermi surface may host a charge density wave (CDW) with concomitant energy gaps. Metallic chain reconstructions on Ge(001) can serve as model systems, such as Au nanowires on Ge(001). In using scanning tunneling microscopy, one finds that the wires are spaced by several Ge lattice constants, with their electron density being laterally strictly confined. In the related system Pt/Ge(001), our data show a conduction path of atomic dimensions [1], yet various dimer elements are detected. In contrast, in Au nanowires the charge density is spread out very evenly in chain direction, as seen for a large range of bias values. This reflects an unusually pronounced delocalization with metallic character at room temperature. Most significantly, at low temperature indication of a periodic superstructure along the chains of twice the unit cell is found. The electronic properties have also been explored with angle-resolved photoemission. These measurements reveal free-electron-like bands close to the Fermi level. Moreover, the observed Fermi level crossings are supportive of a CDW nesting condition. The talk will review the various aspects of this exceptional 1D electron liquid, and present a perspective regarding related systems.
J. Schäfer et al., Phys. Rev. B 74, 041404(R) (2006).