Dresden 2011 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 30: Complex Materials

MM 30.4: Talk

Wednesday, March 16, 2011, 17:00–17:15, IFW D

Order Parameter Dynamics in the quasi two-dimensional Charge Density Wave System 2H−TaSe₂ — •Tim Huber¹, Hanjo Schäfer¹, Helmuth Berger², and Jure Demsar¹ — ¹Physics Department, Universität Konstanz,78457, Germany — ²Institut de Physique de la Matiere Complexe, EPFL, 1015 Lausanne, Switzerland

Recent results of time-resolved spectroscopy on the quasi one-dimensional charge density wave (CDW) system K_0.3MoO₃ have shown that on a short timescale, the electronic and lattice parts of the CDW order parameter are disentangled (Schäfer et al., PRL 105, 066402 (2010)). Here we present the data on the quasi two-dimensional CDW system 2H−TaSe₂ and show - utilizing a time-dependent Ginzburg-Landau model - that they can be interpreted within the same theoretical framework. We demonstrate that also in the quasi two-dimensional case, the appearance of low frequency Raman active modes and their T-dependence can be naturally explained by linear coupling of the electronic part of the order parameter to the 2k_f phonons. Compared to K_0.3MoO₃ , however, in 2H−TaSe₂ the electronic part of the order parameter faster follows the lattice, demonstrated by stronger mode softening as T_c is approached. In addition, we present the first study on Cu-intercalated 2H−TaSe₂ which shows a dramatic increase in the CDW transition temperature compared to its parent compound.