Eur. Phys. J. B 75, 15-22 (2010)
https://doi.org/10.1140/epjb/e2010-00026-5

Electronically driven phase transitions in a quasi-one-dimensional adsorbate system

¹ Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, 6020 Innsbruck, Austria
² Faculty of Physics, University of Vienna, Sensengasse 8, 1090 Vienna, Austria
³ Institute of Applied Physics and Center for Computational Materials Science, Vienna University of Technology, Gußhausstr. 25-25a, 1040 Vienna, Austria
⁴ Institute of Quantum Optics and Quantum Information - Austrian Academy of Sciences, Technikerstr. 21a, 6020 Innsbruck, Austria

Corresponding author: Erminald.bertel@uibk.ac.at

Received: 30 September 2009
Revised: 11 December 2009
Published online: 2 February 2010

Abstract

A quasi-1D system is prepared using the Pt(110) surface as a template. The electronic surface resonance structure is studied by angle-resolved photoemission spectroscopy for the clean surface as well as for different Bromine coverages. A Fermi surface mapping reveals saddle points at the Fermi level in the interior of the surface Brillouin zone. Correspondingly, a maximum in the static response function χ(q, 0) at the connecting vector q is expected. With 1/2G_x < q < 2/3G_x one observes indeed a 3-fold periodicity around defects and a 2-fold periodicity at low temperature for Θ_Br = 0.5 ML. Cooling of a defect-free c(2×2)-Br/Pt(110) preparation counter-intuitively results in a loss of long-range order. Motivated by DFT calculations this is attributed to an anomalous order-order phase transition into the (2×1) phase accompanied by intense, strongly anisotropic fluctuations within a temperature range of ~200 K. The peculiar behaviour is rationalised in terms of a competition between inter-adsorbate repulsion and an adsorbate triggered 2k_F interaction in the substrate.