Anomalous normal state gap in an electron-doped cuprate

TL;DR

This study reveals an anomalous energy gap in underdoped electron-doped cuprates, likely originating from Cooper pairing, which could lead to higher superconducting transition temperatures.

Contribution

It provides evidence of a normal state gap in electron-doped cuprates that connects smoothly to the superconducting gap, suggesting a pairing origin in the underdoped regime.

Findings

Observation of an anomalous energy gap in underdoped cuprates

The gap connects smoothly to the superconducting gap at optimal doping

The normal state gap may originate from Cooper pairing

Abstract

In the underdoped n-type cuprate Nd2-xCexCuO4, long-ranged antiferromagnetic order reconstructs the Fermi surface, resulting in a putative antiferromagnetic metal with small pockets. Using angle-resolved photoemission spectroscopy, we observe an anomalous energy gap, an order of magnitude smaller than the antiferromagnetic gap, in a wide range of the underdoped regime and smoothly connecting to the superconducting gap at optimal doping. After carefully considering all the known ordering tendencies in tandem with the phase diagram, we hypothesize that the normal state gap in the underdoped n-type cuprates originates from Cooper pairing. The high temperature scale of the normal state gap raises the prospect of engineering higher transition temperatures in the n-type cuprates comparable to that of the p-type cuprates.