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 chi(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 I similar to(Br) = 0.5 ML. Cooling of a defect-free c(2x2)-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 (2x1) phase accompanied by intense, strongly anisotropic fluctuations within a temperature range of similar to 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.

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

FRANCHINI, CESARE
Membro del Collaboration Group
;
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 chi(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 I similar to(Br) = 0.5 ML. Cooling of a defect-free c(2x2)-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 (2x1) phase accompanied by intense, strongly anisotropic fluctuations within a temperature range of similar to 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.
2010
Amann P; Cordin M; Braun C; Lechner BAJ; Menzel A; Bertel E; FRANCHINI, CESARE; Zucca R; Redinger J; Baranov M; Diehl S.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/727302
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