Interlayer coherent composite Fermi liquid in Half-filled Landau Level bilayers, a window toward the hidden $\pi$ Berry phase

Understand

For interacting 2D electrons in the presence of magnetic field at half filling, the system forms a `composite Fermi liquid(CFL)' with emergent Fermi surface and exhibits metallic behavior, based on the standard Halperin, Lee, and Read(HLR) field theory.

• Recently, Son introduces a composite Dirac theory as the low energy effective description of Half-filled Landau Level.
• Such theory exhibits particle-hole symmetry and the underlying composite Fermi surface displays a robust $\pi$ Berry phase.
• In this paper, we start from the bilayer Half-filled Landau Level system where the two composite Fermi surface acquires interlayer coherence and forms bonding/anti-bonding composite fermi sea.