Fermi surfaces in Kondo insulators.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Kondo insulators are a class of materials exhibiting unique electronic properties due to strong electron correlations.
• Understanding the electronic structure, particularly the Fermi surface, is crucial for characterizing Kondo insulators.
• YbB₁₂ and SmB₆ are representative examples of Kondo insulators with distinct characteristics.

Purpose of the Study:

• To investigate the electronic structure of the Kondo insulator YbB₁₂ using magnetic quantum oscillations.
• To compare the Fermi surface properties of YbB₁₂ with those of the well-studied Kondo insulator SmB₆.
• To explore potential theoretical models explaining the origin of the bulk Fermi surface in YbB₁₂.

Main Methods:

• Magnetic quantum oscillations were measured using torque magnetometry.
• Complementary measurements included specific heat capacity analysis.
• Comparison with existing data for SmB₆ and theoretical models.

Main Results:

• Observed quantum oscillations and linear specific heat capacity in YbB₁₂ show similarities and differences compared to SmB₆.
• YbB₁₂ exhibits small heavy Fermi surface sections, resembling the heavy fermion semimetallic Fermi surface.
• In contrast, SmB₆ displays large light Fermi surface sections, similar to conduction electron Fermi surfaces.

Conclusions:

• The Fermi surface of YbB₁₂ possesses distinct characteristics compared to SmB₆.
• The findings suggest the presence of novel itinerant quasiparticles that form the bulk Fermi surface.
• These quasiparticles couple to magnetic fields but not to weak DC electric fields, offering avenues for theoretical exploration.