Superfluid density and two-component conductivity in hole-doped cuprates

TL;DR

This paper investigates the complex relationship between the pseudogap, superfluid density, and conductivity in hole-doped cuprates, proposing a two-fluid model to explain superconductivity emergence and its dependence on doping levels.

Contribution

It introduces a two-component conductivity model that links superfluid density with normal state properties, offering new insights into the pseudogap and superconductivity in cuprates.

Findings

Empirical correlations between superfluid density and normal state properties.

Identification of two distinct current-carrying fluids in cuprates.

Superconductivity primarily associated with one fluid that is gapped below pseudogap endpoint.

Abstract

While the pseudogap dominates the phase diagram of hole-doped cuprates, connecting the antiferromagnetic parent insulator at low doping to the strange metal at higher doping, its origin and relation to superconductivity remains unknown. In order to proceed, a complete understanding of how the single hole - initially localized in the Mott state - becomes mobile and ultimately evolves into a coherent quasiparticle at the end of the superconducting dome is required. In order to affect this development, we examine recent transport and spectroscopic studies of hole-doped cuprates across their phase diagram. In the process, we highlight a set of empirical correlations between the superfluid density and certain normal state properties of hole-doped cuprates that offer fresh insights into the emergence of metallicity within the CuO_2 plane and its influence on the robustness of the superconducting state. We conclude by arguing that the overall behavior is best understood in terms of two distinct current-carrying fluids, only one of which dominates the superconducting condensate and is gapped out below the pseudogap endpoint at a critical hole concentration p^\ast.