Charge- and spin-density-wave ordering transitions in strongly correlated metals.

Abstract

We study the quantum transition from a strongly correlated metal, with heavy fermionic quasiparticles, to a metal with commensurate charge or spin density wave order. To this end, we introduce and numerically analyze a large dimensionality model of Ising spins in a transverse field, coupled to two species of fermions; the analysis borrows heavily from recent progress in the solution of the Hubbard model in large dimensions. At low energies, the Ising order parameter fluctuations are characterized by the critical exponent $z \nu = 1$, while above an energy scale, $\Gamma$, there is a crossover to $z\nu = 1/2$ criticality. We show that $\Gamma$ is of the order of the width of the heavy quasiparticle band, and can be made arbitrarily small for a correlated metal close to a Mott-Hubbard insulator. Therefore, such a correlated metal has a significant intermediate energy range of $z\nu=1/2$ behavior, a single particle spectrum with a narrow quasiparticle band, and well-formed analogs of the lower and upper Hubbard bands; we suggest that these features are intimately related in general.