Antiphase Fermi-surface modulations accompanying displacement excitation in a parent compound of iron-based superconductors

TL;DR

This study uses time-resolved photoemission to reveal antiphase oscillations in the electronic structure of BaFe2As2, linked to lattice vibrations and structural changes that relate to superconductivity without doping.

Contribution

It demonstrates the connection between phonon-induced structural modulations and electronic Fermi-surface behavior in a parent superconductor compound.

Findings

Observation of antiphase Fermi-surface oscillations

Link between phonon displacement and Fermi-surface warping

Structural modifications influence superconductivity without doping

Abstract

We investigate the transient electronic structure of BaFe2As2, a parent compound of iron-based superconductors, by time- and angle-resolved photoemission spectroscopy. In order to probe the entire Brillouin zone, we utilize extreme ultraviolet photons and observe photoemission intensity oscillation with the frequency of the A1g phonon which is antiphase between the zone-centered hole Fermi surfaces (FSs) and zone-cornered electron FSs. We attribute the antiphase behavior to the warping in one of the zone-centered hole FSs accompanying the displacement of the pnictogen height, and find that this displacement is the same direction as that induced by substitution of P for As, where superconductivity is induced by a structural modification without carrier doping in this system.