Electronic structure of the alternating monolayer-trilayer phase of La3Ni2O7

TL;DR

This study investigates the electronic structure of the alternating monolayer-trilayer phase of La3Ni2O7 using ARPES, revealing significant differences from the bilayer structure that could influence high-temperature superconductivity.

Contribution

First direct ARPES measurements of the 1313 structure of La3Ni2O7, showing how its electronic structure differs from the bilayer form and highlighting strong correlation effects.

Findings

Presence of a flat band with different binding energy in 1313

Additional electron pocket and band splittings observed

Renormalization factors indicate strong electron correlations

Abstract

Recent studies of La$_3$Ni$_2$O$_7$ have identified a bilayer (2222) structure and an unexpected alternating monolayer-trilayer (1313) structure, both of which feature signatures of superconductivity near 80 K under high pressures. Using angle-resolved photoemission spectroscopy, we measure the electronic structure of 1313 samples. In contrast to the previously studied 2222 structure, we find that the 1313 structure hosts a flat band with a markedly different binding energy, as well as an additional electron pocket and band splittings. By comparison to local-density approximation calculations, we find renormalizations of the Ni-$d_{z^2}$ and Ni-$d_{x^2-y^2}$ derived bands to be about 5 to 7 and about 4 respectively, suggesting strong correlation effects. These results reveal important differences in the electronic structure brought about by the distinct structural motifs with the same stoichiometry. Such differences may be relevant to the putative high temperature superconductivity.