  A theory capable of explaining intrinsic and extrinsic tunnelling conductance
in underdoped cuprates has been devised that accounts for the existence of two
energy scales, their temperature and doping dependencies. The asymmetry and
inhomogeneity seen in extrinsic (normal metal - superconductor (NS)) tunnelling
and the normal-state gapped intrinsic (SS) conductance is explained, as well as
the superconducting gap and normal state pseudogap and the temperature
dependence of the full gap.
