Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 70: Methods: Atomic and Electronic Structure III

O 70.2: Talk

Friday, March 30, 2007, 10:30–10:45, H42

Electronic band structure of the layered dichalcogenide β-MoTe₂ — •Robert Heimburger, Thorsten Zandt, Christoph Janowitz, and Recardo Manzke — Humboldt-Universität zu Berlin, Institut für Physik, Newtonstraße 21, 12489 Berlin

The transition metal dichalcogenide β-MoTe₂ grown by chemical vapour transport (CVT) at temperatures above 1175 K and cooled to room temperature shows a layered structure that can be described as stacked sandwiches of the tree layers Te-Mo-Te. One molybdenium atom is surrounded by six tellurium atoms forming an octahedron which is slightly distorted because of the molybdenium atom beeing displaced from the centre. Therefore strong metal-metal bonds are found which form zigzag chains along the crystallographic b-direction. Upon cooling below 250 K the material undergoes a structural phase transition where the β phase (monoclinic) changes to an orthorhombic Td-structure.
In this contribution we present a detailed temperature dependent study of electronic band structure and Fermi-surface of β-MoTe₂ performed by angle-resolved photoemission spectroscopy (ARPES). The measurements were carried out at BESSY II. It results that the dispersion of the valence bands along the different high-symmetric directions of the Brillouin zone are extremely weak. These bands reveal close insight into the low temperature and phase transition behaviour of quasi-two dimensional materials like β-MoTe₂. Fermi level crossings are studied by Fermi-surface maps. The experimental findings will be compared with tight-binding band structure calculations.