1996/10/17 by Shou-Cheng Zhang · 1 citation
Physics and Astronomy · #cond-mat.supr-con #hep-th
published as Science 275, 1089 (1997) · 36 pages, 1 Postscript figure
arxiv created 1996/10/17 · arxiv updated 2009/11/30
We show that the complex phase diagram of high Tc superconductors can be deduced from a simple symmetry principle, a SO(5) symmetry which unifies antiferromagnetism with d wave superconductivity. We derive the approximate SO(5) symmetry from the microscopic Hamiltonian and show furthermore that this symmetry becomes exact under the renormalization group flow towards a bicritical point. With the help of this symmetry, we construct a SO(5) quantum nonlinear σ model to describe the effective low energy degrees of freedom of the high Tc superconductors, and use it to deduce the phase diagram and the nature of the low lying collective excitations of the system. We argue that this model naturally explains the basic phenomenology of the high Tc superconductors from the insulating to the underdoped and the optimally doped region.