Surprises in the n-type cuprates

The n-type cuprates have long been considered the little cousin of the p-type cuprates, with an apparently simpler phase diagram dominated by antiferromagnetic correlations. Through angle-resolved photoemission spectroscopy (ARPES) studies, we reveal that there are surprises and important insights to be learned from a prototypical n-type cuprate Nd2-xCexCuO4. In the first part of the talk, I will show our recent experimental progress culminating in the observation of Bogoliubov quasiparticles in the n-type cuprates for the first time with ARPES. This reveals that the single low energy cuprate band is fragmented into two sectors of states - AF-reconstructed states that provide the pairing interaction and gossamer states that form the Cooper pairs [1]. In the second part, I will discuss our recent discovery of a new gapped regime in underdoped n-type cuprates [2]. This anomalous normal state gap is formed on the antiferromagnetically reconstructed electron pocket, revealing a similar hierarchy as the pseudogap and superconducting gap in the p-type cuprates. By ruling out antiferromagnetism and charge order, as well as considering its particle-hole symmetry and doping dependence, we deem this gap to be consistent with incoherent pairs with a temperature scale reaching ~150K at low dopings. Our results suggest that the n-type cuprates may have pairing temperature scales comparable to the p-type cuprates.

Speakers: Ke-Jun Ben Xu, Stanford University