Transient gap generation in BaFe₂As₂ driven by coherent lattice vibrations

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Iron-based superconductors exhibit complex interplay between superconductivity, nematicity, and magnetism.
• Pnictogen height critically influences electronic structure and magnetic properties in these materials.
• Previous work suggests laser-driven phonon excitation can modify pnictogen height and magnetic moments.

Purpose of the Study:

• To directly observe the dynamics of Fe magnetic moments and spin-density wave (SDW) gap in BaFe2As2.
• To investigate the impact of coherent $$ phonon excitation on the electronic properties of iron-based superconductors.
• To explore transient phenomena in both superconducting and normal states.

Main Methods:

• Time-resolved broadband terahertz spectroscopy.
• Coherent excitation of the $$ phonon using femtosecond laser pulses.
• Investigation of BaFe2As2 dynamics across different temperature regimes.

Main Results:

• Observed transient gap generation below the SDW transition temperature at early time delays.
• Detected a similar transient feature in the normal state, persisting up to room temperature.
• Provided direct spectroscopic evidence of dynamics influenced by modulated pnictogen height.

Conclusions:

• Coherent phonon excitation can transiently modify the electronic and magnetic properties of iron-based superconductors.
• The observed transient gap generation indicates a dynamic control pathway for these materials.
• The phenomenon is robust, appearing in both superconducting and normal states up to room temperature.