Unconventional Superconductivity in Systems with Annular Fermi Surfaces: Application to Rhombohedral Trilayer...

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Superconductivity in two-dimensional electron gases (2DEGs) with annular Fermi surfaces is a complex phenomenon.
• The role of long-range Coulomb interactions in unconventional superconductivity remains an active area of research.
• Rhombohedral trilayer graphene has recently exhibited superconductivity in specific electronic regimes.

Purpose of the Study:

• To investigate the mechanism driving unconventional superconductivity in 2DEGs with annular Fermi surfaces.
• To explore the influence of Coulomb interactions via the Kohn-Luttinger mechanism.
• To connect theoretical findings to experimental observations in rhombohedral trilayer graphene.

Main Methods:

• Theoretical modeling of electron interactions in a 2D electron gas.
• Application of the Kohn-Luttinger mechanism to systems with annular Fermi surfaces.
• Analysis using realistic parameters for rhombohedral trilayer graphene.

Main Results:

• Long-range Coulomb interactions can induce unconventional superconductivity through the Kohn-Luttinger mechanism.
• Superconductivity is enhanced when inner and outer Fermi surfaces are closely spaced.
• Chiral p-wave, d-wave, and extended s-wave pairing symmetries are identified as possible superconducting states.

Conclusions:

• The proposed Kohn-Luttinger mechanism provides a viable explanation for superconductivity in rhombohedral trilayer graphene.
• The theory accounts for the observed critical temperature (Tc), its dependence on electron density and displacement field.
• It also resolves puzzles like weak temperature-dependent resistivity and proximity to ferromagnetism.