Universal Behavior and the Two-component Character of Magnetically Underdoped Cuprate Superconductors

TL;DR

This paper reviews the scaling behavior of underdoped cuprate superconductors, revealing a two-component system comprising a non-Landau Fermi liquid and a spin liquid, and links these to pseudogap phenomena and superconductivity.

Contribution

It introduces a model mapping the spin liquid component to the 2D Heisenberg model, quantifies doping dependence of key parameters, and explains material differences in superconducting properties.

Findings

Both components decrease linearly with doping level x.

The spin liquid maps onto the 2D Heisenberg model for most temperatures.

Coupling between quasiparticles and spin excitations explains pseudogap and superconductivity.

Abstract

We present a detailed review of scaling behavior in the magnetically underdoped cuprate superconductors (hole dopings less than 0.20) and show that it reflects the presence of two coupled components throughout this doping regime: a non-Landau Fermi liquid and a spin liquid whose behavior maps onto the theoretical Monte Carlo calculations of the 2D Heisenberg model of localized Cu spins for most of its temperature domain. We use this mapping to extract the doping dependence of the strength, $f(x)$ of the spin liquid component and the effective interaction, J_eff(x) between the remnant localized spins that compose it; we find both decrease linearly with x as the doping level increases. We discuss the physical origin of pseudogap behavior and conclude that it is consistent with scenarios in which the both the large energy gaps found in the normal state and their subsequent superconductivity are brought about by the coupling between the Fermi liquid quasiparticles and the spin liquid excitations, and that differences in this coupling between the 1-2-3 and 2-1-4 materials can explain the measured differences in their superconducting transition temperatures and other properties.