BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Physics-TWaP
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-2798
DTSTART:20121008T163000
DURATION:PT1H0M0S
LOCATION:5310 Chamberlin
SUMMARY:Electronic properties of ultimate nanowires\, Condensed Matter Theory Group Seminar\, Franz Himpsel
DESCRIPTION:Stepped semiconductor surfaces decorated with metal atoms make it possible to engineer the ultimate nanowire\, a string of atoms connected by a single wave function. Such atomic wires form spontaneously for many metal-semiconductor combinations and thereby provide a playground for low-dimensional electron physics [1]. Angle-resolved photoelectron spectroscopy combined with scanning tunneling microscopy/spectroscopy reveals a variety of unexpected phenomena\, such as atomically-precise ribbons of graphitic silicon and spin-polarized Fermi surfaces caused by the Rashba effect.<br>
<br>
The broken bond orbitals are so localized at the step edges that they become fully spin-polarized\, similar to isolated broken bonds (Pb centers). Density functional theory predicts a spin-polarized ground state which is closely coupled to the formation of a superlattice (neither can exist without the other) [2]. This resembles the situation in complex oxides (HiTc superconductors\, multiferroics)\, where the spin\, charge\, and lattice degrees of freedom are strongly coupled and make it difficult to find a simple approximation of their electronic structure.<br>
<br>
Two-photon photoemission spectroscopy [3] and scanning tunneling spectroscopy [4] provide support for spin-polarized silicon atoms by probing their characteristic minority spin state. <br>
 <br>
 <br>
REFERENCES<br>
<br>
1.  I. Barke et al.\, <i>Low-dimensional electron gas at semiconductor surfaces</i>\, Solid State Commun. 142\, 617 (2007); <br>
    Nuri Oncel\, <i>Atomic chains on surfaces</i>\, J. Phys. Condens. Matter 20\,  393001 (2008); <br>
    J. Schaefer et al.\, <i>Self-organized atomic nanowires of noble metals on Ge(001): atomic structure and electronic properties</i>\, New Journal of Physics 11\, 125011 (2009);<br>
    P. C. Snijders and H. H. Weitering\, <i>Electronic instabilities in self-assembled atom wires</i>\, Rev. Mod. Phys.  82\, 307 (2010).<br>
2.  S. C. Erwin and F. J. Himpsel\, Intrinsic magnetism at silicon surfaces\, Nature Communications 1:58 (2010).<br>
3.  K. Biedermann et al.\, Spin-split silicon states at step edges of Si(553)-Au\, Phys. Rev. B 85\, 245413 (2012).<br>
4.  P. C. Snijders et al.\, Spectroscopic evidence for spin-polarized silicon atoms on Si(553)-Au\, submitted.<br>
<br>

URL:http://www.physics.wisc.edu/twap/view.php?id=2798
END:VEVENT
END:VCALENDAR