Harvard Condensed Matter Theory Seminars
I discuss an effective theory for the charge 2e sector of
underdoped cuprates, based on the microscopic physics of a
correlated, quantum disordered d-wave superconductor.
The theory describes a superconductor giving way at low doping (x < x_c) to
a ground state with quantum vortex-antivortex fluctuations and
enhanced diamagnetism, but no true superconducting (off-diagonal) order.
At extreme underdoping (x << x_c), the Copper pairs ``disintegrate'',
as charge 2e ``detaches'' from spin-singlet bonds -- the ensuing
ground state is governed by antiferromagnetic (diagonal) rather
than by superconducting (off-diagonal) correlations.
Various features of the theory are evaluated in light of
recent experiments and are used to draw general conclusions about the
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