LONG-RANGE ELECTRON HOPPING AND FERROMAGNETISM IN CLUSTERS

2011 ◽  
Vol 25 (06) ◽  
pp. 747-756 ◽  
Author(s):  
GUANG-HUA LIU ◽  
HAI-LONG WANG ◽  
GUANG-SHAN TIAN
Keyword(s):  
Hubbard Model ◽  
Long Range ◽  
Coulomb Interaction ◽  
Ground State ◽  
Frustration Effect ◽  
Coulomb Repulsion ◽  
Molecular Clusters ◽  
Exact Diagonalization ◽  
Electron Hopping ◽  
Ferromagnetic Ground State

In the present paper, we investigate the frustration effect caused by the long-range electron hopping on ferromagnetism in atomic or molecular clusters. First, for an idealized Hubbard model with constant electron hopping amplitude, we prove rigorously that interplay between such frustration effect and the on-site Coulomb interaction produces the saturated ferromagnetism when the cluster is slightly doped with electron. Then, by exact diagonalization calculation, we study some more realistic clusters and show that the ferromagnetic ground state is still stable as long as the Coulomb repulsion interaction between electrons is sufficiently strong.

scholarly journals Striped phases in the two-dimensional Hubbard model with long-range Coulomb interaction

1998 ◽  
Vol 58 (20) ◽  
pp. 13506-13509 ◽  
Author(s):  
G. Seibold ◽  
C. Castellani ◽  
C. Di Castro ◽  
M. Grilli
Keyword(s):  
Hubbard Model ◽  
Long Range ◽  
Coulomb Interaction ◽  
Two Dimensional ◽  
Striped Phases

scholarly journals Off-Diagonal Long-Range Order in Generalized Hubbard Models

1997 ◽  
Vol 11 (11) ◽  
pp. 1311-1335 ◽  
Author(s):  
Kristel Michielsen ◽  
Hans De Raedt
Keyword(s):  
Density Matrix ◽  
Hubbard Model ◽  
Long Range ◽  
Ground State ◽  
Size Dependence ◽  
State Energy ◽  
System Size ◽  
Range Order ◽  
Long Range Order ◽  
Hubbard Models

We present stochastic diagonalization results for the ground-state energy and the largest eigenvalue of the two-fermion density matrix of the BCS reduced Hamiltonian, the Hubbard model, and the Hubbard model with correlated hopping. The system-size dependence of this eigenvalue is used to study the existence of Off-Diagonal Long-Range Order in these models. We show that the model with correlated hopping and repulsive on-site interaction can exhibit Off-Diagonal Long-Range Order. Analytical results for some special limiting cases indicate that Off-Diagonal Long-Range Order not always implies superconductivity.

scholarly journals Nanograin ferromagnets from nonmagnetic bulk materials: The case of gold nanoclusters

2021 ◽  
pp. 2150148
Author(s):  
Nóra Kucska ◽  
Zsolt Gulácsi
Keyword(s):  
Ground State ◽  
Periodic Boundary ◽  
Gold Nanoclusters ◽  
Coulomb Repulsion ◽  
Periodic Boundary Conditions ◽  
Positive Semidefinite ◽  
Many Body ◽  
Bulk Materials ◽  
Ferromagnetic Ground State ◽  
Spin Orbit Interactions

The ferromagnetism of Au nanograins is analyzed based on a two-dimensional itinerant lattice model with on-site Coulomb repulsion, many-body spin–orbit interactions, and holding two hybridized bands, one correlated and one uncorrelated. Using periodic boundary conditions in both directions, an exact ferromagnetic ground state is deduced for this non-integrable system by applying special techniques based on positive semidefinite operators.

Application of the SD Technique for Solving a BCS-Reduced Hubbard like Hamiltonian

1997 ◽  
Vol 08 (05) ◽  
pp. 1037-1061 ◽  
Author(s):  
Werner Fettes ◽  
Ingo Morgenstern ◽  
Thomas Husslein
Keyword(s):  
Physical Properties ◽  
Hubbard Model ◽  
Detailed Analysis ◽  
Ground State ◽  
Correlation Functions ◽  
Nearest Neighbor ◽  
Exact Diagonalization ◽  
Long Range Order ◽  
Technical Details ◽  
Diagonalization Algorithm

We present exact and stochastic diagonalization results for a BCS-reduced Hubbard model. The kinetic Hamiltonian is the same as in the single band Hubbard model with additional next nearest neighbor hopping. The interaction of this model is designed to inhibit superconductivity in the d x2-y2 channel. The ground state of this model is studied by exact and stochastic diagonalization technique. We present a review of the technical details of the application of the stochastic diagonalization algorithm on this problem. To verify our results obtained with the stochastic diagonalization, they are compared with the exact diagonalization results. In order to show the convergence of the stochastic diagonalization we give a detailed analysis of the behavior of physical properties with increasing number of states. Finally we study superconductivity in this BCS-reduced Hubbard model. As an indicator of superconductivity we use the occurrence of Off Diagonal Long Range Order. We study the scaling behavior of this model for various attractive interactions and in addition the dependence of the superconducting correlation functions from the filling of the system.

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