Electronic properties of ZrTe₃

We present the results of a combined experimental and theoretical study of the electronic structure of ZrTe3. ZrTe3 is a material that undergoes a transition to a charge density wave state at 63 K and displays superconductivity below 2 K. The results of photoemission measurements using synchrotron radiation as well as temperature dependent resistivity and thermopower data allow one to sketch a detailed experimental picture of the electronic structure at the Fermi level. High level TB-LMTO-ASA band structure calculations are used to analyze the bonding situation in ZrTe3 and to relate the physical properties of the crystal to the electronic structure. ZrTe3 is a layered material whose structure is built up from trigonal prismatic ZrTe3 chains with extensive Te-Te interactions perpendicular to the chain direction. These Te-Te interactions lead to wide bands in the direction perpendicular to the chains of trigonal prisms. Frozen phonon calculations indicate that the density of states at the Fermi level and the shape of the Fermi surface are strongly dependent on the Te-Te interprism interactions. The complete computed Fermi surface consists of three independent envelopes: two sheet-like surfaces which are associated with the atoms of the Te, group and a cylindrical section, the former one being responsible for the observed charge density wave properties of ZrTe3. The experimental and calculated nesting vectors for the charge density wave are in excellent agreement. A comparison of the band structures of ZrTe3 with those of the isostructural HfTe3 and ThTe3 reveals that HfTe3 should exhibit similar electronic properties as ZrTe3, whereas ThTe3 should be semimetallic. Based on the results of the frozen phonon calculations, we predict a strong pressure dependence of the physical properties of ZrTe3 and HfTe3