Emergent Dirac fermions in Composite-Fermi-Liquids.

Composite Fermi Liquids (CFLs) are compressible states that can occur for 2D interacting fermions in the lowest Landau level at 1/2m Landau level fillings when m is an integer. They have been understood as Fermi seas of electromagnetic-flux-attached fermions due to Halperin, Lee and Read. At 1/2 filling, an alternative particle-hole symmetric description based on Dirac fermions was proposed by Son. In this talk, we numerically examined the Berry phase associated with transporting one composite fermion around the Fermi sea at filling 1/2 and 1/4. At one-half, a PI Berry curvature singularity was observed [1,2], supporting Son’s effective theory. At one-quarter, we found a uniform Berry curvature and an additional PI strength at Fermi sea center. We explained the 1/4 phenomenon from CFL model wavefunctions. We also proposed a flux-attached Dirac fermion effective action [3], which generalized Son’s theory from 1/2 filling to all other filling fractions. The Fermi-sea in this new theory is interpreted as formed by internal-gauge-flux-attached Dirac fermions.

[1] PRL 121.147202, S. Geraedts, JW, E.H. Rezayi, F.D.M. Haldane.
[2] arXiv 1710.09729, JW, S. Geraedts, E.H. Rezayi, F.D.M. Haldane.
[3] arXiv 1808.09529, JW.