A mean-field approach to Kondo-attractive-Hubbard model

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Investigating the coexistence of magnetic order and superconductivity is crucial for understanding complex electronic phases.
• The interplay between local moments and itinerant electrons influences emergent phenomena in materials.

Purpose of the Study:

• To investigate the coexistence and competition between magnetic order and superconductivity.
• To model the effects of Hubbard (U) and Kondo (J) couplings on electronic phases.
• To provide a qualitative description for borocarbide materials.

Main Methods:

• A model with attractive Hubbard on-site coupling (U) and Kondo-like coupling (J) was studied.
• The model was solved on a simple cubic lattice using Hartree-Fock approximation.
• A semi-classical framework was employed to stabilize spiral magnetic modes.

Main Results:

• Spiral antiferromagnetic (SAFM) states emerge for small U and J.
• A coexistence phase between superconductivity (SC) and SAFM is found upon increasing U.
• Increasing U further leads to a Néel antiferromagnetic state; large J results in a Kondo phase.
• Thermal fluctuations suppress SAFM and SC at finite temperatures, with reentrant behavior observed.

Conclusions:

• The study elucidates the phase diagram, showing transitions between magnetic and superconducting states.
• Competition and coexistence are driven by the interplay of U and J couplings.
• The findings offer a qualitative understanding relevant to borocarbide superconductors.