Superconductor-insulator phase transition in the boson Hubbard model

1993 ◽  
Vol 47 (1) ◽  
pp. 279-286 ◽  
Author(s):  
Arno P. Kampf ◽  
Gergely T. Zimanyi
Keyword(s):  
Phase Transition ◽  
Hubbard Model ◽  
Insulator Phase Transition ◽  
Boson Hubbard Model

scholarly journals Direct detection of metal-insulator phase transitions using the modified Backus-Gilbert method

2018 ◽  
Vol 175 ◽  
pp. 03008 ◽  
Author(s):  
Maksim Ulybyshev ◽  
Christopher Winterowd ◽  
Savvas Zafeiropoulos
Keyword(s):  
Phase Transition ◽  
Hubbard Model ◽  
Order Parameter ◽  
Hexagonal Lattice ◽  
Monte Carlo Algorithm ◽  
Alternative Methods ◽  
Local Order ◽  
Metal Insulator ◽  
Local Order Parameter ◽  
Insulator Phase Transition

The detection of the (semi)metal-insulator phase transition can be extremely difficult if the local order parameter which characterizes the ordered phase is unknown. In some cases, it is even impossible to define a local order parameter: the most prominent example of such system is the spin liquid state. This state was proposed to exist in the Hubbard model on the hexagonal lattice in a region between the semimetal phase and the antiferromagnetic insulator phase. The existence of this phase has been the subject of a long debate. In order to detect these exotic phases we must use alternative methods to those used for more familiar examples of spontaneous symmetry breaking. We have modified the Backus-Gilbert method of analytic continuation which was previously used in the calculation of the pion quasiparticle mass in lattice QCD. The modification of the method consists of the introduction of the Tikhonov regularization scheme which was used to treat the ill-conditioned kernel. This modified Backus-Gilbert method is applied to the Euclidean propagators in momentum space calculated using the hybrid Monte Carlo algorithm. In this way, it is possible to reconstruct the full dispersion relation and to estimate the mass gap, which is a direct signal of the transition to the insulating state. We demonstrate the utility of this method in our calculations for the Hubbard model on the hexagonal lattice. We also apply the method to the metal-insulator phase transition in the Hubbard-Coulomb model on the square lattice.

scholarly journals EFFECT OF A LOCALLY REPULSIVE INTERACTION ON s-WAVE SUPERCONDUCTORS

2010 ◽  
Vol 22 (03) ◽  
pp. 233-303 ◽  
Author(s):  
J.-B BRU ◽  
W. DE SIQUEIRA PEDRA
Keyword(s):  
Phase Transition ◽  
Chemical Potential ◽  
Large Deviation ◽  
Coulomb Repulsion ◽  
Meissner Effect ◽  
Repulsive Interaction ◽  
S Wave ◽  
Insulator Phase Transition ◽  
The One ◽  
Strong Repulsion

The thermodynamic impact of the Coulomb repulsion on s-wave superconductors is analyzed via a rigorous study of equilibrium and ground states of the strong coupling BCS-Hubbard Hamiltonian. We show that the one-site electron repulsion can favor superconductivity at fixed chemical potential by increasing the critical temperature and/or the Cooper pair condensate density. If the one-site repulsion is not too large, a first or a second order superconducting phase transition can appear at low temperatures. The Meißner effect is shown to be rather generic but coexistence of superconducting and ferromagnetic phases is also shown to be feasible, for instance, near half-filling and at strong repulsion. Our proof of a superconductor-Mott insulator phase transition implies a rigorous explanation of the necessity of doping insulators to create superconductors. These mathematical results are consequences of "quantum large deviation" arguments combined with an adaptation of the proof of Størmer's theorem [1] to even states on the CAR algebra.

The character of metal-insulator phase transition in V2O3 from the plasmon behaviour

1983 ◽  
Vol 48 (5) ◽  
pp. 471-474 ◽  
Author(s):  
S Stizza ◽  
I Davoli ◽  
R Bernardini ◽  
A Bianconi ◽  
M Benfatto
Keyword(s):  
Phase Transition ◽  
Metal Insulator ◽  
Insulator Phase Transition

First-principles study on the heterostructure of twisted graphene/hexagonal boron nitride/graphene sandwich structure

2021 ◽  
Author(s):  
Yiheng Chen ◽  
Wen-Ti Guo ◽  
Zi-si Chen ◽  
Suyun Wang ◽  
Jian-Min Zhang
Keyword(s):  
Phase Transition ◽  
Boron Nitride ◽  
Charge Density ◽  
First Principles ◽  
Sandwich Structure ◽  
Hexagonal Boron Nitride ◽  
Mulliken Population ◽  
Metal Insulator ◽  
Insulator Phase Transition ◽  
Twisted Graphene

Abstract In recent years, the discovery of "magic angle" graphene has given new inspiration to the formation of heterojunctions. Similarly, the use of hexagonal boron nitride, known as white graphene, as a substrate for graphene devices has more aroused great interest in the graphene/hexagonal boron nitride (G/hBN) heterostructure system. Based on the first principles method of density functional theory, the band structure, density of states, Mulliken population, and differential charge density of a tightly packed model of twisted graphene/hexagonal boron nitride/graphene (G/hBN/G) sandwich structure have been studied. Through the establishment of heterostructure models TBG inserting hBN with different twisted angles, it was found that the band gap, Mulliken population, and charge density, exhibited specific evolution regulars with the rotation angle of the upper graphene, showing novel electronic properties and realizing metal-insulator phase transition. We find that the particular value of the twist angle at which the metal-insulator phase transition occurs and propose a rotational regulation mechanism with angular periodicity. Our results have guiding significance for the practical application of heterojunction electronic devices.

The metal-insulator phase transition in the strained GdBiTe3

2013 ◽  
Vol 113 (17) ◽  
pp. 17A934 ◽  
Author(s):  
Tran Van Quang ◽  
Miyoung Kim
Keyword(s):  
Phase Transition ◽  
Metal Insulator ◽  
Insulator Phase Transition
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