Disentangling the surface and bulk electronic structures of LaOFeAs

TL;DR

This study uses angle-resolved photoemission spectroscopy to distinguish surface and bulk electronic structures in LaOFeAs, revealing temperature-dependent stability and the effects of surface doping.

Contribution

It provides a detailed analysis of surface versus bulk electronic states in LaOFeAs, combining experimental and theoretical methods to clarify their origins.

Findings

Samples cleaved at low temperature show unstable, complex band structures.

Samples cleaved at high temperature exhibit stable, clearer electronic structures.

Surface doping with potassium helps identify surface states.

Abstract

We performed a comprehensive angle-resolved photoemission spectroscopy study of the electronic band structure of LaOFeAs single crystals. We found that samples cleaved at low temperature show an unstable and highly complicated band structure, whereas samples cleaved at high temperature exhibit a stable and clearer electronic structure. Using \emph{in-situ} surface doping with K and supported by first-principles calculations, we identify both surface and bulk bands. Our assignments are confirmed by the difference in the temperature dependence of the bulk and surface states.