# Evolution of remnant Fermi surface state in lightly-doped correlated spin-orbit insulator Sr$_{2-x}$La$_x$IrO$_4$

## TL;DR

This study investigates how the electronic structure and remnant Fermi surface evolve in lightly-doped Sr$_{2-x}$La$_x$IrO$_4$, revealing similarities with underdoped cuprates and providing insights into the nature of doped correlated spin-orbit insulators.

## Contribution

First detailed ARPES analysis of lightly doped Sr$_2$IrO$_4$ showing the evolution of the remnant Fermi surface and its similarity to cuprate behavior.

## Key findings

- Coexistence of lower Hubbard band and in-gap band observed.
- In-gap state remains anisotropically gapped across momentum space.
- Remnant Fermi surface evolves towards the Fermi energy with doping.

## Abstract

Electronic structure has been studied in lightly electron doped correlated spin-orbit insulator Sr$_2$IrO$_4$ by angle-resolved photoelectron spectroscopy. We have observed coexistence of the lower Hubbard band and the in-gap band, the momentum dependence of the latter traces that of the band calculations without on-site Coulomb repulsion. The in-gap state remained anisotropically gapped in all observed momentum area, forming a remnant Fermi surface state, evolving towards the Fermi energy by carrier doping. These experimental results show a striking similarity with those observed in deeply underdoped cuprates, suggesting the common nature of the nodal liquid states observed in both compounds.