Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 22: Correlated Electrons: Low-dimensional Systems - Materials 1

TT 22.10: Vortrag

Mittwoch, 28. März 2012, 12:00–12:15, H 0104

High-pressure studies of electronic order and lattice dynamics in 1T-TaS₂ — •Tobias Ritschel¹, Jan Trinckauf¹, Jorge Enrique Hamann Borrero¹, Gaston Garbarino², Alexei Bossak², Helmuth Berger³, Martin von Zimmermann⁴, Bernd Büchner¹, and Jochen Geck¹ — ¹Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden), Germany — ²ESRF, Grenoble, France — ³Ecole polytechnique Federale de Lausanne, Switzerland — ⁴HASYLAB, Hamburg, Germany

The layered compound 1T-TaS₂ shows a very complex pressure-temperature phase diagram, including a commensurate (C), a nearly commensurate (NC) and an incommensurate (IC) charge density wave (CDW) phase. In addition, the material exhibits a pressure-induced superconducting phase with T_c ≈ 5 K.

We studied the static CDW-order performed by means of elastic X-ray diffraction as a function of temperature and external pressure. The intensity of the CDW-superlattice reflections within each phase was found to decrease with pressure, while the peak width and the position in reciprocal space was found to remain constant.

Furthermore, we investigated the pressure dependency of the lattice dynamics in the NC and IC phase at room temperature, using inelastic X-ray scattering. The Phonon dispersion around the IC wave vector is strongly pressure dependent and a Kohn anomaly was observed well above the NC to IC phase transition temperature. We will present the experimental data along with model calculations and discuss the results in relation to the pressure-induced superconductivity.