Transient gap generation in BaFe$_2$As$_2$ driven by coherent lattice vibrations

TL;DR

This study uses broadband terahertz spectroscopy to explore how coherent lattice vibrations transiently generate electronic gaps in BaFe$_2$As$_2$, revealing dynamics both below and above the SDW transition temperature.

Contribution

It demonstrates the transient gap generation driven by coherent phonons in BaFe$_2$As$_2$, providing new insights into ultrafast lattice-electronic interactions in iron-based superconductors.

Findings

Transient gap appears below SDW transition temperature.

Similar transient features observed up to room temperature.

Coherent phonon excitation influences electronic structure dynamics.

Abstract

The electronic structure and the magnetic properties of iron-based superconductors are highly sensitive to the pnictogen height. Coherent excitation of the $A_{1g}$ phonon by femtosecond laser directly modulates the pnictogen height, which has been used to control the physical properties of iron-based superconductors. Previous studies show that the driven $A_{1g}$ phonon resulted in a transient increase of the pnictogen height in BaFe$_2$As$_2$, favoring an enhanced Fe magnetic moment. Here, we use time-resolved broadband terahertz spectroscopy to investigate the dynamics of BaFe$_2$As$_2$ in the $A_{1g}$ phonon driven state. Below the spin-density wave (SDW) transition temperature, we observe a transient gap generation at early time delays. A similar transient feature is observed in the normal state up to room temperature.