  The recent observation of quantum oscillations in underdoped high-Tc
superconductors, combined with their negative Hall coefficient at low
temperature, reveals that the Fermi surface of hole-doped cuprates includes a
small electron pocket. This strongly suggests that the large hole Fermi surface
characteristic of the overdoped regime undergoes a reconstruction caused by the
onset of some order which breaks translational symmetry. Here we consider the
possibility that this order is "stripe" order, a form of charge / spin
modulation observed most clearly in materials like Eu-doped and Nd-doped LSCO.
In these materials, the onset of stripe order is indeed the cause of
Fermi-surface reconstruction. We identify the critical doping where this
reconstruction occurs and show that the temperature dependence of transport
coefficients at that doping is typical of metals at a quantum critical point.
We discuss how the pseudogap phase may be a fluctuating precursor of the
stripe-ordered phase.
