Determining the Surface-To-Bulk Progression in the Normal-State Electronic Structure of Sr2RuO4 by Angle-Resolved Photoemission and Density Functional Theory

TL;DR

This study combines high-quality ARPES measurements and density functional theory calculations to investigate the surface and sub-surface electronic structures of Sr2RuO4, revealing a surface-to-bulk progression driven by structural instabilities without evidence of topological or magnetic surface states.

Contribution

It demonstrates that the surface reconstruction extends into sub-surface layers, challenging simpler surface models and clarifying the nature of surface states in Sr2RuO4.

Findings

Surface reconstruction affects multiple layers, not just the top surface.

No evidence of Dirac, Rashba, or magnetic surface states.

Depth-dependent signal degradation indicates a surface-to-bulk progression.

Abstract

In search of the potential realization of novel normal-state phases on the surface of Sr2RuO4 - those stemming from either topological bulk properties or the interplay between spin-orbit coupling (SO) and the broken symmetry of the surface - we revisit the electronic structure of the top-most layers by ARPES with improved data quality as well as ab-initio LDA slab calculations. We find that the current model of a single surface layer (\surd2x\surd2)R45{\deg} reconstruction does not explain all detected features. The observed depth-dependent signal degradation, together with the close quantitative agreement with LDA+SO slab calculations based on the LEED-determined surface crystal structure, reveal that (at a minimum) the sub-surface layer also undergoes a similar although weaker reconstruction. This points to a surface-to-bulk progression of the electronic states driven by structural instabilities, with no evidence for Dirac and Rashba-type states or surface magnetism.