scholarly journals Conductivity in Half-filled Ionic Hubbard Model

2014 ◽  
Vol 24 (3S2) ◽  
pp. 18-22
Author(s):  
Nguyen Danh Tung ◽  
Hoang Anh Tuan
Keyword(s):  
Hubbard Model ◽  
Quantum Monte Carlo ◽  
Coulomb Repulsion ◽  
Finite Conductivity ◽  
Temperature Dependent ◽  
Potential Approximation ◽  
Special Value ◽  
Ionic Hubbard Model ◽  
Ionic Energy ◽  
Good Agreement

We calculate the temperature dependent conductivity in the half-filled ionic Hubbard model with an on-site Coulomb repulsion $U$ and an ionic energy $\Delta$ by mean of the coherent potential approximation. It is shown that for intermediate and large \(\Delta\) the largest conductivity occurs near the special value \(U = 2 \Delta\) at all temperatures \(T\), for a fixed \(\Delta\) the region of finite conductivity \([U_{c1}, U_{c2}]\) expands and its maximum decreases with increasing \(T\). Our results are in good agreement with those derived from the determinant quantum Monte Carlo simulation.

MOTT TRANSITION IN THE HALF-FILLED HUBBARD MODEL ON THE HONEYCOMB LATTICE WITHIN COHERENT POTENTIAL APPROXIMATION

2013 ◽  
Vol 27 (07) ◽  
pp. 1350046 ◽  
Author(s):  
DUC ANH LE
Keyword(s):  
Hubbard Model ◽  
Quantum Monte Carlo ◽  
Mean Field Theory ◽  
Mean Field ◽  
Coulomb Repulsion ◽  
Mott Transition ◽  
Coherent Potential Approximation ◽  
Honeycomb Lattice ◽  
Potential Approximation ◽  
Good Agreement

Using the coherent potential approximation, we study zero-temperature Mott transition in the half-filled Hubbard model on the honeycomb lattice. Although a pseudogap is already present for the non-interacting case, the gap will not occur until the onsite Coulomb repulsion exceeds a critical value U ≈ 3.6t, where t is the hopping integral. When increasing U/t, the density of states at the Fermi energy first goes up gradually from zero and after reaching a maximum it goes down to zero again. Our calculated critical interaction UC/t is in very good agreement with the ones obtained by quantum Monte Carlo simulation and cluster dynamical mean-field theory.

Mott Transition in the Mass Imbalanced Ionic Hubbard Model at Half Filling

2019 ◽  
Vol 29 (3SI) ◽  
pp. 305
Author(s):  
Nguyen Thi Hai Yen ◽  
Le Duc Anh ◽  
Hoang Anh Tuan ◽  
Nguyen Toan Thang
Keyword(s):  
Field Theory ◽  
Hubbard Model ◽  
Mean Field Theory ◽  
Mean Field ◽  
Dynamical Mean Field Theory ◽  
Mass Imbalance ◽  
Half Filling ◽  
Ionic Hubbard Model ◽  
Ionic Energy ◽  
Good Agreement

The Mott - Hubbard metal - insulator transition in the half-filled mass imbalanced ionic Hubbard model is investigated using the two-site dynamical mean field theory. We find that for a fixed mass imbalanced parameter r the critical interaction Uc increases when the ionic energy \(\Delta\) is increased. In the other hand, for a fixed \(\Delta\), \(U_c\) decreases with increasing the mass imbalance. We also show the existence of BI phase in the system for the case \(\Delta \ne 0\), \(U=0\) and calculate the staggered charge density \(n_B − n_A\) as a function of the interaction for different values of the mass imbalance. Our results in the limiting cases (\(r = 1\); \(\Delta \ne 0\) or/and \(\Delta = 0\); \(r\ne 1\)) are in good agreement with those obtained from full dynamical mean field theory.

scholarly journals SUPERCONDUCTIVITY IN THE 2D ATTRACTIVE HUBBARD MODEL WITHIN A FUNCTIONAL FIELD-THEORETICAL RG

2011 ◽  
Vol 25 (28) ◽  
pp. 3691-3706 ◽  
Author(s):  
EBERTH CORREA ◽  
HERMANN FREIRE ◽  
ALVARO FERRAZ
Keyword(s):  
Hubbard Model ◽  
Long Range ◽  
Quantum Monte Carlo ◽  
Mean Field Theory ◽  
Mean Field ◽  
S Wave ◽  
Energy Dynamics ◽  
Attractive Hubbard Model ◽  
Bare Interaction ◽  
Good Agreement

We apply the functional field-theoretical renormalization group methodology up to two-loop order to the 2D attractive Hubbard model for weak bare interaction. Since the momentum-resolved quasiparticle weight ZΛ(p) is always close to unity in the RG flow, higher-order quantum fluctuations do not affect crucially the low-energy dynamics in this case. As a result, we observe a s-wave singlet superconducting quasi-long-range order phase as a function of doping in good agreement with other numerical methods. To assess the role played by the fluctuations we compare the critical temperature Tc in which the quasi-long-range superconducting order phase takes place within our approach with mean-field theory and quantum Monte Carlo results.

PHASE TRANSITION IN THE HALF-FILLED IONIC HUBBARD MODEL: MEAN-FIELD SLAVE BOSON STUDY

2012 ◽  
Vol 26 (03) ◽  
pp. 1150016 ◽  
Author(s):  
DUC-ANH LE ◽  
ANH-TUAN HOANG
Keyword(s):  
Hubbard Model ◽  
Mean Field ◽  
Coulomb Repulsion ◽  
Mott Insulator ◽  
Metallic Phase ◽  
Electronic Phase ◽  
Paramagnetic Solution ◽  
Boson Theory ◽  
Zero Values ◽  
Ionic Hubbard Model

We study electronic phase transitions in the half-filled ionic Hubbard model with an on-site Coulomb repulsion U and an ionic energy Δ by using the Kotliar–Ruckenstein slave-boson theory. Assuming a paramagnetic solution, we show that for any non-zero values of Δ, with increasing U the system undergoes a transition from band-insulator to Mott-insulator. Our results have implied the absence of a metallic phase between the band and the Mott insulator phases.

Analysis of Tempering and Rehardening for Grinding of Hardened Steels

1991 ◽  
Vol 113 (4) ◽  
pp. 388-394 ◽  
Author(s):  
O. B. Fedoseev ◽  
S. Malkin
Keyword(s):  
Thermal Properties ◽  
Heat Source ◽  
Hardened Steel ◽  
Temperature History ◽  
Hardness Distribution ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Reaction Equations ◽  
Rate Controlling Step ◽  
Good Agreement

An analysis is presented to predict the hardness distribution in the subsurface of hardened steel due to tempering and rehardening associated with high temperatures generated in grinding. The grinding temperatures are modeled with a triangular heat source at the grinding zone and temperature-dependent thermal properties. The temperature history, including the effect of multiple grinding passes, is coupled with thermally activated reaction equations for tempering and for reaustenitization which is the rate controlling step in rehardening. Experimental results from the literature are found to be in good agreement with the analytical predictions.

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