ENERGY GAP IN THE HUBBARD MODEL

2000 ◽  
Vol 14 (07) ◽  
pp. 729-735
Author(s):  
L. DIDUKH ◽  
YU. DOVHOPYATY ◽  
YU. SKORENKYY
Keyword(s):  
Hubbard Model ◽  
Single Particle ◽  
Energy Gap ◽  
Particle Energy ◽  
Model Parameters ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Hartree Fock ◽  
New Variant ◽  
Gap Width

A new variant of the generalized Hartree–Fock approximation for calculation of single-particle Green function in the Hubbard model is proposed. The calculated single-particle energy spectrum allows to study metal–insulator transition. Dependences of the energy gap width and the polar states concentration on model parameters are obtained. Conditions of a metallic and an insulating state realisation are found.

scholarly journals ASPECTS OF LOCALIZATION ACROSS THE 2D SUPERCONDUCTOR-INSULATOR TRANSITION

2012 ◽  
Vol 11 ◽  
pp. 22-37
Author(s):  
NANDINI TRIVEDI ◽  
YEN LEE LOH ◽  
KARIM BOUADIM ◽  
MOHIT RANDERIA
Keyword(s):  
Single Particle ◽  
Quantum Monte Carlo ◽  
Energy Gap ◽  
Particle Energy ◽  
Two Dimensions ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Pair Density ◽  
Superconductor Insulator Transition

It is well known that the metal-insulator transition in two dimensions for non-interacting fermions takes place at infinitesimal disorder. In contrast, the superconductor-to-insulator transition takes place at a finite critical disorder (on the order of Vc ~ 2t), where V is the typical width of the distribution of random site energies and t is the hopping scale. In this article we compare the localization/delocalization properties of one and two particles. Whereas the metal-insulator transition is a consequence of single-particle Anderson localization, the superconductor-insulator transition (SIT) is due to pair localization – or, alternatively, fluctuations of the phase conjugate to pair density. The central question we address is how superconductivity emerges from localized single-particle states. We address this question using inhomogeneous mean field theory and quantum Monte Carlo techniques and make several testable predictions for local spectroscopic probes across the SIT. We show that with increasing disorder, the system forms superconducting blobs on the scale of the coherence length embedded in an insulating matrix. In the superconducting state, the phases on the different blobs are coherent across the system whereas in the insulator long-range phase coherence is disrupted by quantum fluctuations. As a consequence of this emergent granularity, we show that the single-particle energy gap in the density of states survives across the transition, but coherence peaks exist only in the superconductor. A characteristic pseudogap persists above the critical disorder and critical temperature, in contrast to conventional theories. Surprisingly, the insulator has a two-particle gap scale that vanishes at the SIT despite a robust single-particle gap.

Single-particle spectral function of a generalized Hubbard model: Metal-insulator transition

1995 ◽  
Vol 51 (20) ◽  
pp. 14012-14019 ◽  
Author(s):  
E. R. Gagliano ◽  
A. A. Aligia ◽  
Liliana Arrachea ◽  
Michel Avignon
Keyword(s):  
Hubbard Model ◽  
Spectral Function ◽  
Single Particle ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Generalized Hubbard Model

The metal-insulator transition in disordered tungsten bronzes. Results of an Anderson-Mott-Hubbard model

1996 ◽  
Vol 205-207 ◽  
pp. 32-42 ◽  
Author(s):  
H. Dücker ◽  
Th. Koslowski ◽  
W. von Messen ◽  
M.A. Tusch ◽  
D.E. Logan
Keyword(s):  
Hubbard Model ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator

scholarly journals Metal-insulator transition in a random Hubbard model

2020 ◽  
Vol 101 (20) ◽  
Author(s):  
Grigory Tarnopolsky ◽  
Chenyuan Li ◽  
Darshan G. Joshi ◽  
Subir Sachdev
Keyword(s):  
Hubbard Model ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator
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