Coherent electronic quasiparticles in the paramagnetic Mott insulator

We study the Mott insulating state of the half-filled paramagnetic Hubbard model within dynamical mean field theory using a recently formulated stochastic and nonperturbative quantum impurity solver. The method is based on calculating the impurity self energy as a sample average over a representative distribution of impurity models solved by exact diagonalization. Due to the natural parallelization of the method, millions of poles are readily generated for the self energy which allows us to work with very small pole-broadening $\ensuremath{\eta}$. Solutions at small and large $\ensuremath{\eta}$ are qualitatively different; solutions at large $\ensuremath{\eta}$ show featureless Hubbard bands whereas solutions at small $\ensuremath{\eta}\ensuremath{\le}0.001$ (in units of half bare band width) show a band of electronic quasiparticles with very small quasiparticle weight at the inner edge of the Hubbard bands. The validity of the results are supported by agreement within statistical error ${\ensuremath{\sigma}}_{\text{QMC}}\ensuremath{\sim}{10}^{\ensuremath{-}4}$ on the imaginary frequency axis with calculations using a continuous time quantum Monte Carlo solver. Nevertheless, convergence with respect to finite size of the stochastic exact diagonalization solver remains to be rigourously established.We study the Mott insulating state of the half-filled paramagnetic Hubbard model within dynamical mean field theory using a recently formulated stochastic and nonperturbative quantum impurity solver. The method is based on calculating the impurity self energy as a sample average over a representative distribution of impurity models solved by exact diagonalization. Due to the natural parallelization of the method, millions of poles are readily generated for the self energy which allows us to work with very small pole-broadening $\ensuremath{\eta}$. Solutions at small and large $\ensuremath{\eta}$ are qualitatively different; solutions at large $\ensuremath{\eta}$ show featureless Hubbard bands whereas solutions at small $\ensuremath{\eta}\ensuremath{\le}0.001$ (in units of half bare band width) show a band of electronic quasiparticles with very small quasiparticle weight at the inner edge of the Hubbard bands. The validity of the results are supported by agreement within statistical error ${\ensuremath{\sigma}}_{\text{QMC}}\ensuremath{\sim}{10}^{\ensuremath{-}4}$ on the imaginary frequency axis with calculations using a continuous time quantum Monte Carlo solver. Nevertheless, convergence with respect to finite size of the stochastic exact diagonalization solver remains to be rigourously established.

arXiv:1404.1885Physical Review BDec 17, 201417 citations

Doublon-holon binding, Mott transition, and fractionalized antiferromagnet in the Hubbard model

Sen Zhou, Yupeng Wang, Ziqiang Wang

We argue that the binding between doubly occupied (doublon) and empty (holon) sites governs incoherent excitations and plays a key role in the Mott transition in strongly correlated Mott-Hubbard systems. We construct a new saddle-point solution with doublon-holon binding in the Kotliar-Ruckenstein slave-boson functional integral formulation of the Hubbard model. On a half-filled honeycomb lattice and square lattice, the ground state is found to exhibit a continuous transition from a paramagnetic semimetal/metal to an antiferromagnetic-ordered Slater insulator with coherent quasiparticles at ${U}_{c1}$ , followed by a Mott transition into an electron-fractionalized AF ${}^{*}$ phase without coherent excitations at ${U}_{c2}$ . Such a phase structure appears to be generic for bipartite lattices without frustration. We show that doublon-holon binding unites the three important ideas of strong correlation: coherent quasiparticles, incoherent Hubbard bands, and deconfined Mott insulator.We argue that the binding between doubly occupied (doublon) and empty (holon) sites governs incoherent excitations and plays a key role in the Mott transition in strongly correlated Mott-Hubbard systems. We construct a new saddle-point solution with doublon-holon binding in the Kotliar-Ruckenstein slave-boson functional integral formulation of the Hubbard model. On a half-filled honeycomb lattice and square lattice, the ground state is found to exhibit a continuous transition from a paramagnetic semimetal/metal to an antiferromagnetic-ordered Slater insulator with coherent quasiparticles at ${U}_{c1}$, followed by a Mott transition into an electron-fractionalized AF${}^{*}$ phase without coherent excitations at ${U}_{c2}$. Such a phase structure appears to be generic for bipartite lattices without frustration. We show that doublon-holon binding unites the three important ideas of strong correlation: coherent quasiparticles, incoherent Hubbard bands, and deconfined Mott insulator.

arXiv:1302.5427Physical Review BMay 15, 201430 citations

Electronic state of a doped Mott-Hubbard insulator at finite temperatures studied using the dynamical mean-field theory

Alberto Camjayi, R. Chitra, Marcelo J. Rozenberg

We study the electronic state of the doped Mott-Hubbard insulator within the dynamical mean field theory. The evolution of the finite temperature spectral functions as a function of doping show large redistributions of spectral weight in both antiferromagnetic and paramagnetic phases. In particular, a metallic antiferromagnetic state is obtained with a low frequency Slater-splitted quasiparticle peak coexisting with Hubbard bands. In the high temperature paramagnetic metallic phase, upon reducing doping, the system has a crossover through a ``bad metal'' state characterized by an anomalous shift of the quasiparticle peak away from the Fermi energy. We find that the charge compressibility of the antiferromagnetic metal is dramatically enhanced upon approaching the second order N\'eel line.We study the electronic state of the doped Mott-Hubbard insulator within the dynamical mean field theory. The evolution of the finite temperature spectral functions as a function of doping show large redistributions of spectral weight in both antiferromagnetic and paramagnetic phases. In particular, a metallic antiferromagnetic state is obtained with a low frequency Slater-splitted quasiparticle peak coexisting with Hubbard bands. In the high temperature paramagnetic metallic phase, upon reducing doping, the system has a crossover through a ``bad metal'' state characterized by an anomalous shift of the quasiparticle peak away from the Fermi energy. We find that the charge compressibility of the antiferromagnetic metal is dramatically enhanced upon approaching the second order N\'eel line.

arXiv:cond-mat/0604155Physical Review BJan 19, 200618 citations

{U}_{c1}

, followed by a Mott transition into an electron-fractionalized AF

{}^{*}

phase without coherent excitations at

{U}_{c2}

. Such a phase structure appears to be generic for bipartite lattices without frustration. We show that doublon-holon binding unites the three important ideas of strong correlation: coherent quasiparticles, incoherent Hubbard bands, and deconfined Mott insulator.