Fermi surface and pseudogap in highly doped Sr$_{2}$IrO$_{4}$

TL;DR

This study uses ARPES to explore the electronic structure of highly doped Sr$_{2}$IrO$_{4}$, revealing a persistent pseudogap and Fermi surface fragmentation, indicating a unique phase with coexisting large Hall density and anisotropic pseudogap.

Contribution

It provides new insights into the pseudogap phase and Fermi surface evolution in highly doped Sr$_{2}$IrO$_{4}$, extending previous doping levels and revealing persistent pseudogap behavior.

Findings

Pseudogap persists up to highest doping level studied.

Fermi surface breaks into disconnected arcs.

Pseudogap temperature is about 200 K, similar to cuprates.

Abstract

The fate of the Fermi surface in bulk electron-doped Sr$_{2}$IrO$_{4}$ remains elusive, as does the origin and extension of its pseudogap phase. Here, we use high-resolution angle-resolved photoelectron spectroscopy (ARPES) to investigate the electronic structure of Sr$_{2-x}$La$_{x}$IrO$_{4}$ up to $x=0.2$, a factor of two higher than in previous work. We find that the antinodal pseudogap persists up to the highest doping level, and thus beyond the sharp increase in Hall carrier density to $\simeq 1+x$ recently observed above $x^{*}\simeq 0.16$ [Y.-T. Hsu et al., Nature Physics 20, 1593 (2024)]. This suggests that doped iridates host a unique phase of matter in which a large Hall density coexists with an anisotropic pseudogap, breaking up the Fermi surface into disconnected arcs. The temperature boundary of the pseudogap is $T^{*}\simeq 200$ K for $x=0.2$, comparable to cuprates and to the energy scale of short range antiferromagnetic correlations in cuprates and iridates.