SC state in the underdoped high-T_c cuprates as a quantum spin liquid. A microscopic theory

摘要

We have discovered a new example of quantum spin liquid which is asuperconducting (SC) phase in 2D electron system close to electronictopological transition. As a quantum spin liquid in low dimensional localizedspin systems it is characterized by a resonance spin mode and a well separatedtwo-particle continuum. Application of the theory to the high-T_c cupratesallows to shed light on many observed in the underdoped regime features such asthe so called 40 meV resonance peak, incommensurability at lower \omega, spingap etc.