Neutron Spin Resonance in the 112-Type Iron-Based Superconductor

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Iron-based superconductors exhibit complex magnetic and electronic properties.
• Understanding spin excitations is crucial for elucidating superconductivity mechanisms.

Purpose of the Study:

• Investigate low-energy spin excitations in the iron pnictide Ca_{0.82}La_{0.18}Fe_{0.96}Ni_{0.04}As_{2}.
• Characterize the nature and origin of the observed spin resonance mode.

Main Methods:

• Inelastic neutron scattering (INS) was employed to probe spin excitations.
• Polarized neutron analysis was utilized to determine spin and orbital characteristics.

Main Results:

• A two-dimensional spin resonance mode was observed at approximately 11 meV.
• The resonance energy showed temperature independence and scaled linearly with the critical temperature (Tc).
• Polarized neutron data indicated the resonance is spin-isotropic and lacks magnetic modulations.

Conclusions:

• The spin resonance energy and momentum distribution are independent of the k_z fermiology.
• The spin resonance is identified as a spin-1 mode arising from singlet-triplet Cooper pair excitations.
• This finding provides insights into the interplay between spin dynamics and superconductivity in iron-based materials.