Fractionalized Fermi liquids

TL;DR

In spatial dimensions d>or=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 (rho(a)-1)(mod 2), with rho( a) the mean number of all electrons per unit cell of the ground state.

Abstract

In spatial dimensions d >= 2, Kondo lattice models of conduction and local moment electrons can exhibit a fractionalized, non-magnetic state (FL*) with a Fermi surface of sharp electron-like 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 Z_2 gauge case. The FL* state permits a second order metamagnetic transition in an applied magnetic field.

Figures (1)

• Figure 1: Mean field phase diagram of $H$ on the triangular lattice. We used fermionic representations of Sp($N$) for the spins, and restricted attention, by hand, to saddle points which preserve all lattice symmetries. We had nearest-neighbor $t=1$, $J_H=0.4$, and $\rho_c=0.7$. The superconducting $T_c$ is exponentially small, but finite, for large $J_K$, while it is strictly zero for small $J_K$. Thin (thick) lines are second (first) order transitions. The transitions surrounding the superconductor will survive beyond mean field theory, while the others become crossovers.