Publications (8)11.79 Total impact
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ABSTRACT: Dynamics in a triangularlattice Hubbard model is studied at half filling on the basis of the cluster dynamical mean field theory. Numerical calculations use a solver of the continuoustime quantum Monte Carlo method based on the strongcoupling expansion. We examine the change in the nearestneighbor dynamical correlations of doublon and holon in the time domain with varying the Coulomb repulsion near the Mott transition. We demonstrate that the nearestneighbor doublonholon pair shows a strong attractive correlation, particularly in the insulating phase, while the nearestneighbor doublondoublon pair shows a repulsive correlation. Useful information is provided by the trajectories in the complex plane of the dynamical correlation functions. The shorttime dynamics of the nearestneighbor doublon and holon in the metallic phase indicates larger fluctuations than in the insulating phase. Their trajectories in the complex plane show that the shorttime dynamics of the doublonholon pair has an opposite behavior to that of the doublondoublon pair. We find that their time scale of dynamics can be characterized by the period in which the phase rotates π around the longtime limit in both phases. In the longtime region, fluctuations persist up to a very long time in the metallic phase, while they quickly vanish in the insulating phase.  [Show abstract] [Hide abstract]
ABSTRACT: We study the dynamics of doublon in the halffilled Hubbard model on the triangular lattice by using the cellular dynamical mean field theory. Investigating the nearestneighbor dynamical correlations, we demonstrate that a nearestneighbor doublonholon pair shows a strong attraction, in particular in the insulating phase. We also calculate the onsite dynamical correlation of doublon and find that the life time of doublon is longer in the metallic phase than in the insulating phase. In the longtime region, the metallic phase has persistent fluctuations in various nearestneighbor configurations, while the fluctuations are vanishingly small in the insulating phase. Obtained results indicate clear differences of dynamics of doublon between in the metallic and in the insulating phases.  [Show abstract] [Hide abstract]
ABSTRACT: We numerically study electric transport near the Mott metalinsulator transition for the halffilled Hubbard model on a triangular lattice. Our approach is a cellular dynamical mean field theory (CDMFT) with a continuoustime QMC solver and we calculate optical conductivity including vertex corrections. The main issue is the variation of optical conductivity upon controlling Coulomb repulsion U for various temperatures. Near the Mott critical end point, a Drude peak on the metallic side smoothly continues to an ``ingap" peak emerging within the Hubbard gap on the insulating side. We find a critical powerlaw behavior in their Udependence near the critical point. The obtained critical exponent 1/δ=0.15 of the optical weight differs from the exponent 1/δ=1/3 of the order parameter (double occupancy) in the CDMFT calculations. This discrepancy suggests that conductivity does not have the same scaling behavior as that for the order parameter[1]. [1]T. Sato, K. Hattori, and H. Tsunetsugu, J. Phys. Soc. Jpn. 81, 083703 (2012).  [Show abstract] [Hide abstract]
ABSTRACT: We study electric transport near the Mott metalinsulator transition in a triangularlattice Hubbard model at half filling. We calculate optical conductivity $\sigma(\omega)$ based on a cellular dynamical mean field theory including vertex corrections inside the cluster. Near the Mott critical end point, a Drude analysis in the metallic region suggests that the change in the Drude weight is important rather than that in the transport scattering rate for the Mott transition. In the insulating region, there emerges an "ingap" peak in $\sigma(\omega)$ at low $\omega$ near the Mott transition, and this smoothly connects to the Drude peak in the metallic region with decreasing Coulomb repulsion. We find that the weight of these peaks exhibits a powerlaw behavior upon controlling Coulomb repulsion at the critical temperature. The obtained critical exponent suggests that conductivity does not correspond to magnetization or energy density of the Ising universality class in contrast to several previous works.  [Show abstract] [Hide abstract]
ABSTRACT: We examine the validity of the projected GrossPitaevskii simulation by taking the twodimensional homogeneous bosonic system as an example. The longdistance behaviors of the correlation function and equilibrium temperatures show good agreement with those of the quantum Monte Carlo calculations below temperatures near the KosterlitzThouless transition. We find that in the projected GrossPitaevskii description, one needs to estimate the optimal wavenumber cutoff in temperature. In the welldescribed region, the projected GrossPitaevskii equation presents reliable predictions for the longwave bosonic components.  [Show abstract] [Hide abstract]
ABSTRACT: We study electric transport near the Mott metalinsulator transition. Optical conductivity of the halffilled Hubbard model on a triangular lattice is calculated based on a cellular dynamical mean field theory including vertex corrections inside the cluster. By investigating the spectrum at low frequencies, we find that a Drude peak on the metallic side smoothly connects to an "ingap" peak on the insulating side. The optical weight of these peaks exhibits a critical behavior with powerlaw near the Mott critical end point, $DD^*\proptoUU^*^{1/\delta}$. We find that the critical exponent $1/\delta$ differs from the exponents in the thermodynamics.  [Show abstract] [Hide abstract]
ABSTRACT: We study optical conductivity of the oneband Hubbard model on a twodimensional isotropic triangular lattice at half filling by using the cellular dynamical mean field theory and particularly investigate its behavior near the critical end point of the first order Mott transition. In the metallic phase, the enhancement of effective mass and the significant frequency dependence of scattering rate is identified near the Mott transition. From the results in the insulating state near the Mott transition, we find that the frequency dependence of optical conductivity decays quite smoothly toward zero frequency and exhibits a powerlawlike behavior in an intermediate frequency region. We also study optical conductivity of the Hubbard model on a kagomé lattice near the critical end point of the Mott transition. It shows a larger incoherent peak both in the metallic and insulating phases and a stronger frequency dependence of effective mass and scattering rate.  [Show abstract] [Hide abstract]
ABSTRACT: We study the finitetemperature transition of the quasi2D Bose gas in an uniaxiallycompressed harmonic trap by numerically solving the projected GrossPitaevskii equation. Gradual emergence of superfluidity is confirmed by calculating the moment of inertia when a temperature decreases. By investigating the longdistance behavior of a phase correlation function, superfluid density gradually increases reflecting the development of the phase correlation around the center of the system. From these results, we obtain the evidence for the emergence of superfluidity in this system directly.
Publication Stats
15  Citations  
11.79  Total Impact Points  
Top Journals
Institutions

20142015

RIKEN
 Computational Condensed Matter Physics Laboratory
Вако, Saitama, Japan


20092012

The University of Tokyo
 Institute for Solid State Physics
Edo, Tōkyō, Japan
