You will be redirected to the full text document in the repository in a few seconds, if not click here. Similarly, the attractive hubbard model has been used to explore qualitative features of the superconducting phase transition. Destruction of superconductivity by impurities in the. Anderson first proposed that the strongcoupling version of the hubbard model could explain hightemperature superconductors 26. Transport and optical conductivity in the hubbard model.
J like models exhibit d wave super conductivity for certain parameters 6 10. Optical conductivity in a twodimensional extended hubbard. Robert schrieffer, which is known as the bcs theory. Hubbard model fh with two kinds of particles with opposite spins. The central feature of the bcs theory is that two electrons in the superconductor are able to form a bound pair called a cooper pair if they somehow experience an attractive interaction between. Contrary to the above mentioned papers, the selfenergy operators due to. Shortrange antiferromagnetic correlations are known to open a spin gap in the repul sive hubbard model on ladders with m legs, when m is. Bedtttf 2 i 3 using the mean field theory and the nakanokubo formula.
Optical conductivity obtained through dqmc and maxent analytic continuation forthe hubbard model with parametersu t6. Pdf superconductivity with s and psymmetries in an. Electron doping and superconductivity in the twodimensional. Elsevier physica b 230232 1997 10371040 unconventional superconductivity in the hubbard holstein model takashi hotta, yasutami takada institute for solid state physics, university of tokyo 7221 roppongi, minatoku, tokyo 106, japan abstract properties of the groundstate wave function is studied for the halffilled hubbard holstein model with two and four sites by the exact.
Iii, the rg equations are derived using the operator product expansion to one loop. We study the superconducting pairing correlations in the ground state of the doped hubbard model in its original. The existence of dwave superconductivity in the hubbard model has been demonstrated by perturbative analytic calculations 4 later improved by renormalization group methods 5, 6 and by numerics 7, 8. The importance of conductivity conductivity measurement is an extremely widespread and useful method, especially for quality control purposes. Coherence lengths for superconductivity in the twoorbital. Ii, we introduce the nchain hubbard model, its weakcoupling limit, and a compact currentalgebra notation for the allowed interactions. Superexchange, or kramersanderson superexchange, is the strong usually antiferromagnetic coupling between two nexttonearest neighbour cations through a nonmagnetic anion. Several different models have recently been proposed to explain high temperature superconductivity. Pdf coexistence of superconductivity and antiferromagnetism in. Calculations within the dynamical mean field approximation dmfa 10 can be performed in the strong coupling regime and take place in the thermodynamic limit. There is a belief that they are actually interrelated and not mutually exclusive, although a convincing demonstration of any such connection is yet to be found.
We investigate numerically the ground state of the 1d extended hubbard model, with onsite interaction u and nearestneighbor interaction v. Super conductivity with dwave symmetry turns out to be restricted to densities where the fermi surface crosses the magnetic zone boundary. Determinant quantum monte carlo study of exciton condensation. Superconductivity and antiferromagnetism in the twodimensional. A marked asymmetry is found between the localized holedoped region and the more itinerant electrondoped region. Because the interband excitation is characteristic in a twodimensional dirac electron system, a peak structure is found above the charge order gap. Absence of superconductivity in the pure twodimensional hubbard.
Ferromagnetism and superconductivity in twoband hubbard. J model 3 and the asymmetric hubbard model 6 by applying the projection technique to the gf 10 in terms of the hubbard operators. With increasing ut there is, however, a very interesting metalinsulator transition predicted11 to occur around ut. In this way, it differs from direct exchange in which there is coupling between nearest neighbor cations not involving an intermediary anion. In addition, comparisons will be made with the other numerical approaches to the hubbard model and the numerical results on the t j model. We first discuss the properties of the model within the mean.
Our model connects the two to the threedimensional case, and it spans four fermi surface. Himeda and ogata found it in a variational monte carlo study of thetj model 12. Physics of the hubbard model and high temperature superconductivity. Estimates of effective hubbard model parameters for c20 isomers.
From the hubbard model to high temperature superconductivity. Phase transitions of the ionic hubbard model on the honeycomb. The optical conductivity in the charge order phase is calculated in the twodimensional extended hubbard model describing an organic dirac electron system. It is a model of interest in connection with the theory of hightc super conductivity 8, and it can be used to describe bound states of electron and holes in some nanostructures as nanorings excitons 9. This method may also have applications to understanding the conductivity in models that display manybody localization 35,36. Do antiferromagnetic fluctuations induce dwave superconductivity. Our starting point will be the bcs theory, but specialized to the hubbard model. Pdf superconductivity and the pseudogap in the two. We consider a tightbinding singleband model with a minimal henrik. The repulsive hubbard model has long served as a simple hamiltonian to describe itinerant magnetism. A simple mechanism and model for unconventional superconductivity. The hubbard model has a long history in describing the magnetism of materials since the early works by hubbard 26, gutzwiller 68 and kanamori 69. W, necessary for the experimentally observed mott hubbard insulator at half filling.
Dupuis3 1maxplanck institute for solid state research, heisenbergstr. Hubbard model and that is the driving force of pair formation and also of their condensation. A microscopic theory of superconductivity was developed in 1957 by john bardeen, leon cooper and j. Introduction to onedimensional hubbard model on the origin of the hubbard model origin of the hubbard model i model named after john hubbard describes electronic correlations in narrow energy band metals starting from the model. One dimensional hubbard model has been well understood by.
Effect of disorder on chargedensity wave and superconducting. Superconductivity and antiferromagnetism in the two. Phase diagram of the attractive hubbard model with. Pdf superconductivity in the hubbard model with pair hopping. As a result, attention has focused on a more realistic extended hubbard model that includes both cu and 0 orbitals with local and nearest neighbor repulsive interactions 3, 41. The key parameters for controlling the mott physics are the electronic bandfilling and bandwidth. Above the superconducting critical temperature, an analog of. These approaches are complementary for each other in dimensionality and expected to give us reliable results beyond the perturbative or the mean. Condensed matter physics twodimensional groundstate mapping. But the lack of nonlocal correlations inhibits a transition to. How does the fermi surface evolve with loss of antiferromagnetism. Unconventional superconductivity in the hubbardholstein model. Absence of superconductivity in the 1d extended hubbard model.
Effect of longrange hopping on tc in a twodimensional. The hubbard model, named after john hubbard, is the simplest model of interacting particles in a lattice, with only two terms in the hamiltonian see example below. Shown are the data for various temperaturest 1b, where we have set boltzmannsconstantk b 1. Introduction the electron correlation in solids, or the mott physics, offers intriguing phenomena in materials such as unconventional super conductivity sc. We focus v u, u t at quarter filling, where previous studies suggested the possibility of dominant superconducting pairing fluctuations before phase separation at a critical value v v ps. Magnetism and superconductivity in the twoband hubbard model. Weakcoupling superconductivity in an anisotropic three.
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