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 7.5: Hauptvortrag (ohne Erstattung)

Montag, 25. Februar 2008, 12:30–13:00, HE 101

Electronic instabilities and fluctuations in quantum chains — •Hanno H. Weitering — Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN 37931, USA — Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

One-dimensional (1D) quantum conductors have always captured the imagination of physicists. While a strictly 1D material remains a theoretical construct, a vast number of materials can be viewed as macroscopic ensembles of weakly-coupled quantum chains, making them interesting test cases for theoretical predictions. I will discuss the electronic and magnetic properties of some quasi 1D systems on Si and Ge surfaces. Highlights include the remarkable self-assembly of rare-earth metal atoms on Si into silicide nanowires. Large strain anisotropy in these wires can lead to extraordinary aspect ratios and uniformity. The thinnest wires exhibit electronic properties reminiscent of a multi-channel 1D conductor. These include the stepwise increase of the tunnel current as a function of tip bias in scanning tunneling microscopy, and the appearance of a fluctuating charge density wave or Peierls instability at low temperature. Peierls instabilities are normally attributed to a collective screening response of the 1D electron gas, but in the present case there is no obvious connection to the classical Peierls picture. The remarkable assembly of yttrium atoms into long nanowires with built-in metal/semiconductor junctions is illustrative of how the finite-size- and temperature-scaling behavior of a collective phenomenon may one day be exploited in nano-architectures.