Dispersion kinks from electronic correlations in an unconventional iron-based superconductor.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Conventional superconductors rely on bosonic modes for attractive interactions, but the pairing mechanism in unconventional superconductors remains largely unknown.
• Electron-boson coupling is crucial for understanding unconventional superconductors, with dispersion kinks in spectral functions serving as a key experimental signature.
• Dispersion kinks indicate abrupt changes in quasiparticle velocity and lifetime, offering insights into the underlying interactions.

Purpose of the Study:

• To investigate the origin of dispersion kinks in the unconventional iron-based superconductor RbFe2As2.
• To explore the role of electron-boson coupling and many-body interactions in this material.
• To establish a connection between iron-based superconductors and other classes of correlated materials.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) was employed to probe the electronic structure and identify dispersion kinks.
• Dynamical mean-field theory (DMFT) was utilized to model the strong correlation effects and many-body interactions.
• Analysis of the spectral function to observe changes in quasiparticle properties.

Main Results:

• Two distinct dispersion kinks were observed in the electronic spectral function of RbFe2As2.
• Evidence for the formation of a Hubbard band multiplet, arising from Coulomb interaction and Hund's rule coupling in the multiorbital system.
• The identified dispersion kinks were demonstrated to be a direct consequence of these strong many-body interactions.

Conclusions:

• The study confirms that strong many-body interactions, including Coulomb and Hund's rule coupling, are responsible for the observed dispersion kinks in RbFe2As2.
• These findings provide a unifying perspective, linking the behavior of iron-based superconductors to other correlated unconventional superconductors.
• The results support theoretical predictions for dispersion kinks in various models of correlated materials.