  In the underdoped n-type cuprate Nd2-xCexCuO4, long-ranged antiferromagnetic
order reconstructs the Fermi surface, resulting in a putative antiferromagnetic
metal with small pockets. Using angle-resolved photoemission spectroscopy, we
observe an anomalous energy gap, an order of magnitude smaller than the
antiferromagnetic gap, in a wide range of the underdoped regime and smoothly
connecting to the superconducting gap at optimal doping. After carefully
considering all the known ordering tendencies in tandem with the phase diagram,
we hypothesize that the normal state gap in the underdoped n-type cuprates
originates from Cooper pairing. The high temperature scale of the normal state
gap raises the prospect of engineering higher transition temperatures in the
n-type cuprates comparable to that of the p-type cuprates.
