Perturbation study of nonequilibrium quasiparticle spectra in an infinite-dimensional Hubbard lattice

A model for nonequilibrium dynamical mean-field theory is constructed for the infinite-dimensional Hubbard lattice. We impose nonequilibrium by expressing the physical orbital as a superposition of a left (L) -moving and right (R) -moving electronic state with the respective chemical potentials μL and μR. Using the second-order iterative perturbation theory we calculate the quasiparticle properties as a function of the chemical potential bias between the L and R movers, i.e., Φ= μL - μR. The evolution of the nonequilibrium quasiparticle spectrum is mapped out as a function of the bias and temperature. The quasiparticle states with the renormalized Fermi-energy scale ε QP 0 disappear at Φ∼ ε QP 0 in the low-temperature limit. The second-order perturbation theory predicts that in the vicinity of the Mott-insulator transition at the Coulomb-parameter U= Uc, there exists another critical Coulomb-parameter Ud (< Uc) such that, for Ud <U< Uc, quasiparticle states are destroyed abruptly when (ε QP 0) 2 ∼a (π kB Tc) 2 +b Φc2 with the critical temperature Tc, the critical bias Φc, and the numerical constants a and b on the order of unity.