Fermi-surface transformation across the pseudogap critical point of the cuprate superconductor La${}_{1.6-x}$Nd${}_{0.4}$Sr${}_x$CuO${}_4$

Abstract

The electrical resistivity $\ddot{I}$ and Hall coefficient R${}_H$ of the tetragonal single-layer cuprate Nd-LSCO were measured in magnetic fields up to $H=37.5$ T, large enough to access the normal state at $T\to 0$, for closely spaced dopings $p$ across the pseudogap critical point at $p^{\star }=0.235$. Below $p^{\star }$, both coefficients exhibit an upturn at low temperature, which gets more pronounced with decreasing $p$. Taken together, these upturns show that the normal-state carrier density $n$ at $T=0$ drops upon entering the pseudogap phase. Quantitatively, it goes from $n=1+p$ at $p=0.24$ to $n=p$ at $p=0.20$. By contrast, the mobility does not change appreciably, as revealed by the magneto-resistance. The transition has a width in doping and some internal structure, whereby R${}_H$ responds more slowly than $\ddot{I}$ to the opening of the pseudogap. We attribute this difference to a Fermi surface that supports both hole-like and electron-like carriers in the interval $0.2<p<p^{\star }$, with compensating contributions to R${}_H$. Our data are in excellent agreement with recent high-field data on YBCO and LSCO. The quantitative consistency across three different cuprates shows that a drop in carrier density from $1+p$ to $p$ is a universal signature of the pseudogap transition at $T=0$. We discuss the implication of these findings for the nature of the pseudogap phase.

11 pages, 12 figures