Direct evidence for a competition between the pseudogap and high temperature superconductivity in the cuprates

TL;DR

This study provides direct evidence that in cuprates, the pseudogap and high-temperature superconductivity compete, with the pseudogap depleting spectral weight and hindering the development of superconducting coherence.

Contribution

It demonstrates through ARPES measurements that the pseudogap and superconductivity are competing orders, clarifying their relationship in high-Tc cuprates.

Findings

Pseudogap reduces low-energy spectral weight.

Superconducting coherence is limited to parts of the Fermi surface.

Pseudogap and superconductivity compete, affecting high-Tc properties.

Abstract

A pairing gap and coherence are the two hallmarks of superconductivity. In a classical BCS superconductor they are established simultaneously at Tc. In the cuprates, however, an energy gap (pseudogap) extends above Tc. The origin of this gap is one of the central issues in high temperature superconductivity. Recent experimental evidence demonstrates that the pseudogap and the superconducting gap are associated with different energy scales. It is however not clear whether they coexist independently or compete. In order to understand the physics of cuprates and improve their superconducting properties it is vital to determine whether the pseudogap is friend or foe of high temperature supercondctivity. Here we report evidence from angle resolved photoemission spectroscopy (ARPES) that the pseudogap and high temperature superconductivity represent two competing orders. We find that there is a direct correlation between a loss in the low energy spectral weight due to the pseudogap and a decrease of the coherent fraction of paired electrons. Therefore, the pseudogap competes with the superconductivity by depleting the spectral weight available for pairing in the region of momentum space where the superconducting gap is largest. This leads to a very unusual state in the underdoped cuprates, where only part of the Fermi surface develops coherence.