Fractionalized Fermi Liquids

In spatial dimensions d≥2, Kondo lattice models of conduction and local moment electrons can exhibit a fractionalized, nonmagnetic state (FL^*) with a Fermi surface of sharp electronlike quasiparticles, enclosing a volume quantized by (ρ_a-1)(mod 2), with ρ_a the mean number of all electrons per unit cell of the ground state. Such states have fractionalized excitations linked to the deconfined phase of a gauge theory. Confinement leads to a conventional Fermi liquid state, with a Fermi volume quantized by ρ_a(mod 2), and an intermediate superconducting state for the Z₂ gauge case. The FL^* state permits a second order metamagnetic transition in an applied magnetic field.