Kondo resonance for orbitally degenerate systems

Area of Science:

• Condensed Matter Physics
• Quantum Many-Body Theory

Background:

• The Kondo effect describes the interaction between localized magnetic moments and conduction electrons.
• The standard Anderson model is a key theoretical framework for studying the Kondo state.
• Extending these models to multiple bands is crucial for understanding complex materials.

Purpose of the Study:

• Investigate the formation of the Kondo state in a general two-band Anderson model.
• Analyze the behavior of the Abrikosov-Suhl resonance under different conditions.
• Examine the impact of external magnetic fields on the Kondo state.

Main Methods:

• Numerical renormalization group (NRG) calculations were employed.
• The study focused on the quarter filling case (one electron per impurity).
• External magnetic (or pseudomagnetic) fields were applied to break degeneracy.

Main Results:

• The Abrikosov-Suhl resonance exhibits essential asymmetry in the two-band model, differing from the one-band case.
• An external field causes asymmetric splitting and significant broadening of the many-body resonance.
• The 'spin-up' Kondo peak remains pinned at the Fermi level and is not suppressed by the magnetic field.

Conclusions:

• The two-band Anderson model presents distinct Kondo physics compared to the single-band model.
• Magnetic fields significantly alter the resonance structure but do not suppress the pinned Kondo peak.
• These findings offer insights into the behavior of strongly correlated electron systems.