Survey of the Thermodynamic Properties of the Charge Density Wave Systems

Figure 6

Color on line. Temperature dependence of the measured relative velocity ∆V/V as a function of the reduced temperature . Velocity of the longitudinal mode in the (a b) plane in TiSe₂ [20], 2H-TaS₂ [16, 17], 2H-NbSe₂ [16, 17], and TTF-TCNQ [36]. Velocity of the mode C₃₃ measured with ErTe₃ at the upper CDW phase transition T_CDW = 260 K [42]. The dashed curves are calculated with the BCS theory (see (14)).