Fermi-surface reconstruction and two-carrier model for the Hall effect in YBa2Cu4O8

Pulsed field measurements of the Hall resistivity and magnetoresistance of underdoped YBa2Cu4O8 are analyzed self-consistently using a simple model based on coexisting electron and hole carriers. The resultant mobilities and Hall numbers are found to vary markedly with temperature. The conductivity of the hole carriers drops by one order of magnitude below 30 K, explaining the absence of quantum oscillations from these particular pockets. Meanwhile the Hall coefficient of the electron carriers becomes strongly negative below 50 K. The overall quality of the fits not only provides strong evidence for Fermi-surface reconstruction in Y-based cuprates, it also strongly constrains the type of reconstruction that might be occurring. A key step to unraveling the mystery of high-temperature superconductivity in the cuprates is an elucidation of the nature of the normal state from which the superconductivity emerges and its evolution with doping. At half filling, the cuprate plane is insulating and antiferromagnetically ordered. With increasing hole doping, antiferromagnetism is suppressed and superconductivity first rises, then diminishes. Beyond the superconducting dome, a highly correlated Fermi liquid with a large Fermi surface FS is recovered. 1 The nature of the intermediate state lying between these two extremes however remains an outstanding and controversial issue. Angle-resolved photoemission spectroscopy ARPES suggests the existence of Fermi arcs, disjointed lines of lowlying excitations centered along the zone diagonals, in the underdoped UD regime. 2‐4 The nodal arc picture implies a gradual destruction of the FS or decoherence of quasiparticle states with increasing correlation strength due to the formation of an anisotropic pseudogap that is peaked at the zone boundaries. Quantum oscillation QO experiments, meanwhile, suggest a very different scenario for the ground state of UD cuprates involving closed pockets, not lines, of coherent excitations. 5‐11 Coupled with the observation of a negative Hall effect RH Ref. 12 and thermopower 13 at low T, a picture then emerges in which the large holelike FS seen on the overdoped OD side undergoes symmetry-breaking reconstruction into electron e and hole h pockets or sheets at a critical doping level pc. 14