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 μ_L and μ_R. 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=μ_L−μ_R. 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_QP⁰ disappear at Φ∼ε_QP⁰ 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=U_c, there exists another critical Coulomb-parameter U_d (<U_c) such that, for U_d<U<U_c, quasiparticle states are destroyed abruptly when (ε_QP⁰)²∼a(πk_BT_c)²+bΦ_c² with the critical temperature T_c, the critical bias Φ_c, and the numerical constants a and b on the order of unity.