  Besides the usual conductance plateaus at multiples of 2e2/h, quantum point
contacts typically show an extra plateau at ~ 0.7(2e2/h), believed to arise
from electron-electron interactions that prohibit the two spin channels from
being simultaneously occupied. We present evidence that the disappearance of
the 0.7 structure at very low temperature signals the formation of a Kondo-like
correlated spin state. Evidence includes a zero-bias conductance peak that
splits in a parallel field, scaling of conductance to a modified Kondo form,
and consistency between peak width and the Kondo temperature.
