Temperature dependence of the mid-infrared dielectric function of YBCO in the a–b plane: a re-evaluation

Frequency and temperature dependence of ac loss and scaling study of a high-temperature cuprate superconductor

“…This time, all the data (for different frequencies) in the normal state collapsed on a universal curve. A similar kind of normal state scaling is observed for the other samples (figures [12][13][14]. In determining the characteristic temperature (T S ), initially we take the T S as the available pseudogap temperature (T G ) value from other workers [16,17] and subsequently we try to obtain the best fit for the master curve varying T S around the initial value.…”

“…The complex permeability is an important parameter for studying ac loss [11], as its imaginary part is responsible for the losses due to the absorption of the ac field. Many groups [12][13][14][15] have studied the frequency-and temperature-dependent dielectric properties of HTSC samples to extract valuable information regarding the ac loss mechanism. The real part of the ac conductivity (σ 1 ) is proportional to energy dissipation.…”

The mid-infrared dielectric function of NBCO in thea-bplane from 85 K to 300 K

“…Extensive studies have been made of the frequency and temperature dependence of the optical conductivity of the cuprate superconductors with a view to understanding their carrier dynamics [17][18][19][20][21][22][23][24]. The bulk of this work has been on YBCO in the far-IR [17], but much attention has also been focused on the anomalous mid-IR region, where there is little or no temperature dependence in the conductivity [17][18][19][20][21]24].…”

“…Extensive studies have been made of the frequency and temperature dependence of the optical conductivity of the cuprate superconductors with a view to understanding their carrier dynamics [17][18][19][20][21][22][23][24]. The bulk of this work has been on YBCO in the far-IR [17], but much attention has also been focused on the anomalous mid-IR region, where there is little or no temperature dependence in the conductivity [17][18][19][20][21]24]. In optimally oxygenated NBCO and YBCO, the normal-state dc resistivity rises linearly with increasing temperature, a response indicative of metallic behaviour and therefore consistent with current transport by free carriers.…”

“…However, a simple Drude model has been unable to explain the observed optical properties of the normal-state cuprates, such as YBCO. Whereas the optical conductivity (σ r ) at frequencies in the far-IR (50-300 cm −1 ) increases with temperature, the conductivity in the mid-IR has been shown to be largely temperature independent [17,24]. Our raw dielectric results are analysed in terms of the generalized Drude model for carrier dynamics in metallic-like materials [25].…”