Interplay of Externally Doped and Thermally Activated Holes in ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ and Their Impact on the Pseudogap Crossover

We presented the recent Hall effect data for a number of carriers in ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ as the sum of two components: the temperature independent term $n_0(x)$, which is due to external doping, and the thermally activated contribution. Their balance determines the crossover temperature $T^{*}(x)$ from the marginal Fermi liquid to pseudogap regime. The activation energy $\Delta (x)$ for thermally excited carriers equals the energy between the Fermi surface “arc” and the band bottom, as seen in angle-resolved photoemission spectroscopy experiments. Other implications for the ($T$, $x$)-phase diagram of cuprates are also discussed.

Figure 1

The doping dependence of $n_0(x)$, obtained by the fitting of Eq. (1) to the experimental Hall coefficient temperature dependence [8, 14, 17, 18] for LSCO.

Figure 2

The activation energy $\Delta (x)$ obtained by the fitting of Eq. (1) to the experimental Hall coefficient temperature dependence [8, 14, 17, 18] for LSCO (open circles and triangles), vs the energy separating the underlying vH bands from the Fermi level (binding energy) which was deduced from Fig. 3(b) of 4 and Fig. 3 in 16 for various $x$ (solid circles).

Figure 3

The PG crossover temperature $T^{*}(x)$ obtained with the help of Eq. (1) with the activation energy $\Delta (x)$ shown in Fig. 2 (solid circles); from the crossover temperature of the resistivity curves (open circles); as the temperature ($T_m$) corresponding to the maximum of the magnetic susceptibility measured in 23 (solid triangles) and 24 (open triangles).