Fractionalization in the cuprates: Detecting the topological order
  The precise theoretical characterization of a fractionalized phase in spatial dimensions higher than one is through the concept of ``topological order''. We describe a physical effect that is a robust and direct consequence of this hidden order that should enable a precise experimental characterization of fractionalized phases. In particular, we propose specific ``smoking-gun'' experiments to unambiguously settle the issue of electron fractionalization in the underdoped cuprates. 
T. Senthil and Matthew P.A. Fisher