We study quantum phase transitions of an ionic Hubbard model in two dimensions. The ionic Hubbard model explains the quantum states of strongly correlated electrons under the influence of checkerboard-type alternating chemical potentials. For a given amplitude of the alternating potentials Δ, we obtain quantum ground states as we tune the local repulsive energy U between a spin-up electron and a spin-down electron by using an exact diagonalization method of a modified Lanczos algorithm. The system undergoes a quantum phase transition from a band insulator to a Mott insulator as U increases at half-filling. We find the signature of a quantum phase transition by investigating the behavior of ground-state energies and that of double occupancies for the size of L × L = 4 × 4, which was the largest possible lattice in this work. We compare our results with those of quantum Monte Carlo simulations employing the Hirsch-Fye algorithm.We study quantum phase transitions of an ionic Hubbard model in two dimensions. The ionic Hubbard model explains the quantum states of strongly correlated electrons under the influence of checkerboard-type alternating chemical potentials. For a given amplitude of the alternating potentials Δ, we obtain quantum ground states as we tune the local repulsive energy U between a spin-up electron and a spin-down electron by using an exact diagonalization method of a modified Lanczos algorithm. The system undergoes a quantum phase transition from a band insulator to a Mott insulator as U increases at half-filling. We find the signature of a quantum phase transition by investigating the behavior of ground-state energies and that of double occupancies for the size of L × L = 4 × 4, which was the largest possible lattice in this work. We compare our results with those of quantum Monte Carlo simulations employing the Hirsch-Fye algorithm.

Journal of the Korean Physical SocietyMar 1, 20172 citations

Quantum Monte Carlo studies of density functional theory

Maziar Nekovee, W. M. C. Foulkes, Richard J. Needs

Mathematics and Computers in SimulationMar 1, 20032 citations

Quantum Monte Carlo study of bilayer ionic Hubbard model

Mi Jiang, T. C. Schulthess

The interaction-driven insulator-to-metal transition has been reported in the ionic Hubbard model (IHM) for moderate interaction $U$ , while its metallic phase only occupies a narrow region in the phase diagram. To explore the enlargement of the metallic regime, we extend the ionic Hubbard model to two coupled layers and study the interplay of interlayer hybridization $V$ and two types of intralayer staggered potentials $\mathrm{\ensuremath{\Delta}}$: one with the same (in-phase) and the other with a $\ensuremath{\pi}$-phase shift (antiphase) potential between layers. Our determinant quantum Monte Carlo (DQMC) simulations at lowest accessible temperatures demonstrate that the interaction-driven metallic phase between Mott and band insulators expands in the $\mathrm{\ensuremath{\Delta}}\text{\ensuremath{-}}V$ phase diagram of bilayer IHM only for in-phase ionic potentials; while antiphase potential always induces an insulator with charge density order. This implies possible further extension of the ionic Hubbard model from the bilayer case here to a realistic three-dimensional model.The interaction-driven insulator-to-metal transition has been reported in the ionic Hubbard model (IHM) for moderate interaction $U$, while its metallic phase only occupies a narrow region in the phase diagram. To explore the enlargement of the metallic regime, we extend the ionic Hubbard model to two coupled layers and study the interplay of interlayer hybridization $V$ and two types of intralayer staggered potentials $\mathrm{\ensuremath{\Delta}}$: one with the same (in-phase) and the other with a $\ensuremath{\pi}$-phase shift (antiphase) potential between layers. Our determinant quantum Monte Carlo (DQMC) simulations at lowest accessible temperatures demonstrate that the interaction-driven metallic phase between Mott and band insulators expands in the $\mathrm{\ensuremath{\Delta}}\text{\ensuremath{-}}V$ phase diagram of bilayer IHM only for in-phase ionic potentials; while antiphase potential always induces an insulator with charge density order. This implies possible further extension of the ionic Hubbard model from the bilayer case here to a realistic three-dimensional model.

Physical review. B./Physical review. BApr 28, 20166 citations

Analytical Wavefunctions from Quantum Monte Carlo Simulations

Dario Bressanini, Pietro Cremaschi, Massimo Mella +1 more

Recent advances in computationalMay 1, 19971 citation

Quantum Monte Carlo Simulations

Matthias Troyer, Philipp Werner, Adolfo Avella +1 more

AIP conference proceedingsJan 1, 200914 citations

The interaction-driven insulator-to-metal transition has been reported in the ionic Hubbard model (IHM) for moderate interaction

U

, while its metallic phase only occupies a narrow region in the phase diagram. To explore the enlargement of the metallic regime, we extend the ionic Hubbard model to two coupled layers and study the interplay of interlayer hybridization

V

and two types of intralayer staggered potentials $\mathrm{\ensuremath{\Delta}}$: one with the same (in-phase) and the other with a $\ensuremath{\pi}$-phase shift (antiphase) potential between layers. Our determinant quantum Monte Carlo (DQMC) simulations at lowest accessible temperatures demonstrate that the interaction-driven metallic phase between Mott and band insulators expands in the $\mathrm{\ensuremath{\Delta}}\text{\ensuremath{-}}V$ phase diagram of bilayer IHM only for in-phase ionic potentials; while antiphase potential always induces an insulator with charge density order. This implies possible further extension of the ionic Hubbard model from the bilayer case here to a realistic three-dimensional model.