Constant effective mass across the phase diagram of high-T$_{c}$ cuprates

TL;DR

This study shows that in high-Tc cuprates, the effective mass of holes remains constant across the phase diagram, indicating a vanishing carrier number transition to the Mott insulator, which impacts understanding of their transport and pairing.

Contribution

It provides evidence that the effective mass does not increase in the underdoped regime, challenging theories that predict mass enhancement near the Mott transition.

Findings

No substantial mass enhancement in underdoped cuprates.

Transition to Mott insulator involves vanishing carrier number.

Effective mass remains constant across the phase diagram.

Abstract

We investigate the hole dynamics in two prototypical high temperature superconducting systems: La$_{2-x}$Sr$_{x}$CuO$_{4}$ and YBa$_{2}$Cu$_{3}% $O$_{y}$ using a combination of DC transport and infrared spectroscopy. By exploring the effective spectral weight obtained with optics in conjunction with DC Hall results we find that the transition to the Mott insulating state in these systems is of the "vanishing carrier number" type since we observe no substantial enhancement of the mass as one proceeds to undoped phases. Further, the effective mass remains constant across the entire underdoped regime of the phase diagram. We discuss the implications of these results for the understanding of both transport phenomena and pairing mechanism in high-T$_{c}$ systems.