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

TL;DR

This paper proposes a microscopic theory identifying a superconducting phase in underdoped high-T_c cuprates as a quantum spin liquid, explaining various experimental features observed in these materials.

Contribution

It introduces a new quantum spin liquid model for the superconducting phase in underdoped cuprates, linking it to observed spectral features.

Findings

Explains the 40 meV resonance peak in cuprates

Accounts for incommensurability at lower energies

Describes the spin gap phenomenon

Abstract

We have discovered a new example of quantum spin liquid which is a superconducting (SC) phase in 2D electron system close to electronic topological transition. As a quantum spin liquid in low dimensional localized spin systems it is characterized by a resonance spin mode and a well separated two-particle continuum. Application of the theory to the high-T_c cuprates allows to shed light on many observed in the underdoped regime features such as the so called 40 meV resonance peak, incommensurability at lower \omega, spin gap etc.