Figure 1
(Color online) Optical data for YBCO and both optical and transport data for LSCO discussed in the context of the high-
phase diagram. Left panels are data for
LSCO and right panels depict the low temperature optical conductivity as a function of doping for both LSCO and YBCO. Data in panels (f)–(h) are at
and at
just above
in panels (e). Panel (a): phase diagram with the values shown for LSCO; the yellow area is the long range AF region (denoted by
), the green area is the superconducting region (marked by
), and the pseudogap region is denoted by
. To facilitate a direct comparison with the data, temperature is plotted on the horizontal axis and doping on the vertical axis. The Hall coefficient
displayed in panel (b) reveals two characteristic regimes (I and II). This is exemplified for the
sample but similar behavior is found for all heavily underdoped crystals. These regimes can also be identified with significant regions in the dc resistivity corrected for thermal expansion (c). Panel (d): the effective number of carriers,
, determined from the optical data as described in the text. Right panels: the real part of the conductivity at low temperature [
, except
for (e) and (f) and
for
], displayed as black solid curves. Red colors signify fits using the standard Drude model. The blue area is a subtraction of the Drude fit from
and is referred to as the “mid-infrared contribution” throughout the text. The resonant structure in the latter contribution can be adequately described with a Lorentzian oscillator (dashed lines). The loss function
, panels (i), also clearly depicts two components (shown as red and blue curves) for dopings
, and the progression to a single component, (black solid curve) for higher dopings.
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