  We report measurements of multi-path transport through a triple quantum dot
(TQD) in the few-electron regime using a GaAs three-terminal device with a
separate lead attached to each dot. When two paths reside inside the transport
window and are simultaneously spin-blockaded, the leak currents through both
paths are significantly enhanced. We suggest that the transport processes in
the two paths cooperate to lift the spin blockade. Fine structures in transport
spectra indicate that different kinds of cooperative mechanisms are involved,
depending on the details of the three-electron spin states governed by the size
of exchange splitting relative to nuclear spin fluctuations. Our results
indicate that a variety of correlation phenomena can be explored in
three-terminal TQDs.
