Interlayer coherent composite Fermi liquid in Halffilled Landau Level bilayers, a window toward the hidden $\pi$ Berry phase
Abstract
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 Halffilled Landau Level. Such theory exhibits particlehole symmetry and the underlying composite Fermi surface displays a robust $\pi$ Berry phase. In this paper, we start from the bilayer Halffilled Landau Level system where the two composite Fermi surface acquires interlayer coherence and forms bonding/antibonding composite fermi sea. The corresponding interlayer coherent composite Fermi liquid(ICCFL) phase provides a straightforward landscape to verify the Dirac nature in Son's theory and extract the hidden Berry phase structure of the composite Fermi surface. The ICCFL phase contains two Fermi surfaces which are detached in most regions but adhesive at two hot spots. Such nematic structure is a consequence of the Berry phase encoded in the Dirac Fermi surface which is absent in HLR theory. Due to the nematicity in ICCFL, the system supports halfquantum vortex with deconfined $\frac{\pi}{2}$ gauge flux and the phase transition toward ICCFL contains a Lifshitz criticality with $z=3$ dynamical exponent. In addition, the exciton order parameter carries topological spin number so the ICCFL contains a unique WenZee term which connects EM response with the background geometry curvature.
 Publication:

arXiv eprints
 Pub Date:
 April 2017
 arXiv:
 arXiv:1704.03463
 Bibcode:
 2017arXiv170403463Y
 Keywords:

 Condensed Matter  Strongly Correlated Electrons;
 High Energy Physics  Theory