Surface and bulk electronic structures of LaOFeAs studied by angle resolved photoemission spectroscopy

TL;DR

This study uses angle-resolved photoemission spectroscopy to analyze the surface and bulk electronic structures of LaOFeAs, revealing how electronic bands evolve across structural and magnetic transitions and identifying surface state characteristics.

Contribution

It provides detailed insights into the bulk and surface electronic structures of LaOFeAs, highlighting band shifts and reconstructions associated with phase transitions, and discusses surface state behaviors.

Findings

Bulk band shifts by about 25 meV across the SDW transition

Surface states show small band shifts reflecting bulk reconstruction

Sharp quasiparticle peaks emerge at low temperatures indicating reduced scattering

Abstract

The electronic structure of LaOFeAs, a parent compound of iron-arsenic superconductors, is studied by angleresolved photoemission spectroscopy. By examining its dependence on photon energy, polarization, sodium dosing and the counting of Fermi surface volume, both the bulk and the surface contributions are identified. We find that a bulk band moves toward high binding energies below structural transition, and shifts smoothly across the spin density wave transition by about 25 meV. Our data suggest the band reconstruction may play a crucial role in the spin density wave transition, and the structural transition is driven by the short range magnetic order. For the surface states, both the LaO-terminated and FeAs-terminated components are revealed. Certain small band shifts are verified for the FeAs-terminated surface states in the spin density wave state, which is a reflection of the bulk electronic structure reconstruction. Moreover, sharp quasiparticle peaks quickly rise at low temperatures, indicating of drastic reduction of the scattering rate. A kink structure in one of the surface band is shown to be possibly related to the electron-phonon interactions.