Doping dependence of the normal-state Hall coefficient in YBCO

We report on the doping dependence of the normal-state Hall coefficient $R_{\rm H}(T)$ in the high-Tc superconductor $\rm YBa_2Cu_3O_y$ for $0.08 < p < 0.15$, measured in magnetic fields up to 60 T. $R_{\rm H}(T)$ is seen to drop below a temperature $T_{\rm H}$, to become negative at low temperature, as previously reported for two dopings (1). We attribute this drop to a reconstruction of the Fermi-surface caused by the onset of broken translational symmetry, which produces an electron-like pocket in the Fermi surface of underdoped YBCO. The fact that $T_{\rm H}$ peaks at $p = 1/8$ strongly suggests that Fermi-surface reconstruction is caused by stripe order. (1) D. LeBoeuf et al., Nature 450, 533 (2007).