Optical conductivity spectra

Fig. 3. Reflectivity (a) and optical conductivity spectra (b) of oriented CNTs films along the an and aj directions. Bruggeman (BM) and Maxwell-Garnett (MG) fits (see text and Table 2) are also presented.

This suggests an intrinsic metallic behaviour of the single CNTs. In this respect. Fig. 12 presents the intrinsic reflectivity (a) and optical conductivity spectra (b) of a hypothetical "bulk" (i.e., / = 1) CNTs specimen, using the parameters of Table 2. The low frequency metallic behaviour is easily recognised. (The reflectivity tends to 100 % when the frequency goes to zero and... 

Fig. 1. Optical conductivity spectra of AXC60 (x = 0, 3, 4, and 6) [7]. K3C60 is a metal, which shows a Drude-like behavior at low energy region, while K4C6o is an insulator, which does not show such a behavior.

Figure 3. Optical conductivity spectra of p -BEDO-TTF)5[CsHg(SCN)4]2 for E L L and E L at 300, 200, 100 and 10 K (L is BEDO-TTF stack direction). The fit with Drude-Lorenz model for T=10 K is shown by thin solid line.

The behaviour of the polarized reflectivity and optical conductivity spectra of new quasi-two-dimensional organic conductor p -(BEDO-TTF)5[CsHg(SCN)4]2 versus temperature for E L and E1. L are quite different. For E . L, the temperature changes of R(ro) and ct(co) are due to the decrease of the optical relaxation constant of the free carriers as expected for a metal. For E L at temperatures below 200 K, the energy gaps in the ct(co) spectra at about 4000 cm 1 and at frequencies below 700 cm 1 appear simultaneously with the two new bands of ag vibrations of the BEDO-TTF molecule activated by EMV coupling. This suggests a dimerization of the BEDO-TTF molecules in the stacks, which leads to a metal-semiconductor transition.. In the direction perpendicular to L, the studied salt shows metallic properties due to a very favourable overlap of the BEDO-TTF molecular orbitals. 

Fujishima et al. [95] used optical-conductivity spectra to monitor the increase in effective mass of the electrons with La concentration. Kumagai et al. [96] measured the electronic specific heat y at low temperatures and compared it to the magnetic susceptibility x obtained by Tokura et al. [97] on the same samples see Fig. 21. The Wilson ratio //y remained nearly constant over the entire range of x, which indicates that the divergence of y and x on... 

Fig. 2. (top) Optical conductivity spectra of Lai-xSrxTiOs and Yi-xCaxTiOs as a function of changing bandfilling n (=1 - x) (from [74]). (bottom) Effective number of carriers Neu as a function of x for Yi-xCaxTiOs (left) and effective mass parameter F = m /m - 1 as a function of bandfilling (right) [65]... 

Fig. 4. (top) Phase diagram for high Tc cuprates, (bottotn) Optical conductivity spectra left) and effective niunber of carriers Neff i ight) of La2-xSrxCu04 for various x [84]... 

Fig. 5. (top) Optical conductivity spectra, bottom) Absorption maximum, comaxy n/m ( Neff), and mass enhancement factor, X, of Bai xKxBi03 for various x [136]... 

Fig. 8. (top) Optical conductivity spectra for NdNiOa at various temperatures, (bottom) Effective number of carriers Neff and the magnetic moment as a function of temperature [157]... 

Fig. 9. Optical conductivity spectra of Ca2Ru04 (Ca214), CaaRuaOy (Ca327), and SraRuaOy (Sr327) [164]...

Figure 7.3 Optical conductivity spectra in (a) La2 xSrjcCu04 [27] and (b) Lai cSr cMn03 with x = 0.175 [28]. The inset in (b) shows a magnification...

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