  There are several ways to turn a superconductor into a normal conductor:
increase the temperature, apply a high magnetic field, or run a large current.
High-T$_c$ cuprate superconductors are unusual in the sense that experiments
suggest that destroying superconductivity by heating the sample to temperatures
above T$_c$ or by applying a high magnetic field result in different 'normal'
states. Spectroscopic probes show that above T$_c$, in the pseudogap regime,
the Fermi surface is partly gapped and there are no well-defined
quasiparticles. Transport measurements, on the contrary, reveal quantum
oscillations in high magnetic fields and at low temperatures, suggesting a more
usual Fermi liquid state. Studying the electronic structure while suppressing
superconductivity by using current, will hopefully shed new light on this
problem. In type II superconductors, such as the cuprates, the resistive state
created by the current is a result of vortex motion. The large dissipation in
the flux-flow regime makes spectroscopic measurements in the presence of
current challenging. We performed angle-resolved photoemission experiments in
thin films of Bi$_2$Sr$_2$CaCu$_2$O$_y$ while running high-density current
through the samples. Clear evidence was found for non-uniform flux flow,
leaving most of the sample volume free of mobile vortices and dissipation. The
super-current changes the electronic spectrum, creating quasiparticle and
quasihole pockets. The size of these pockets as a function of the current is
found to be doping dependent; it depends both on the superfluid stiffness and
on the strength of interactions.
