Multiple-pseudogap phases in hydrogen-doped LaFeAsO system

TL;DR

This study investigates the electronic pseudogap phenomena in hydrogen-doped LaFeAsO, revealing two distinct pseudogap phases associated with its two superconducting domes and their evolution with doping.

Contribution

It provides the first detailed doping-dependent analysis of pseudogap behavior in LaFeAsO1-xHx using laser photoemission spectroscopy, highlighting two distinct pseudogap phases.

Findings

Pseudogap suppresses with doping in the first dome

Pseudogap strengthens with doping in the second dome

Pseudogap correlates with antiferromagnetic order

Abstract

The low energy electronic structure of LaFeAsO1-xHx (0.0 < x < 0.60), the system which exhibits two superconducting domes in its phase diagram, is investigated by utilizing the laser photoemission spectroscopy. From the precise temperature-dependent measurement of the spectra near the Fermi level, we find the suppression of the density of states with cooling, namely the pseudogap formation, for all doping range. The pseudogap in the low x range (i.e. the first superconducting dome regime) gets suppressed with increasing x, more or less similarly to the previous results in F-doped LaFeAsO system. On the other hand, the pseudogap behavior in the second superconducting dome regime at high-x becomes stronger with increasing the H-doping level. The systematic doping dependence shows that the pseudogap is enhanced toward the both ends of the phase diagram where the different types of antiferromagnetic order exist.