We study effect of inhomogeneities of the lattice in the S = 1/2 bondalternating chain by using a quantum Monte Carlo method and an exact diagonalization method. We adopt a defect in the alternating order as the inhomogeneity and we call it ‘‘bond impurity’’. Local magnetic structures induced by the bond impurities are investigated both in the ground state and

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 dx2−y2 channel. The ground state of this model is studied by exact and stochastic diagonalization technique. We...

A new approach to large-scale nuclear structure calculations, based on the Density Matrix Renormalization Group (DMRG), is described. The method is tested in the context of a problem involving many identical nucleons constrained to move in a single large-j shell and interacting via a pairing plus quadrupole interaction. In cases in which exact diagonalization of the hamiltonian is possible, the...

The molecular solids $\beta^\prime$-$X$[Pd(dmit)$_2$]$_2$ (where $X$ represents a cation) are typical compounds whose electronic structures described by single-orbital Hubbard-type Hamiltonians with geometrical frustration. Using the $ab$ $initio$ downfolding method, we derive low-energy effective for available room- and low-temperature structures. We find that amplitudes of Coulomb interaction...

We present numerical studies of fermion and boson models with random all-to-all interactions (the SYK models). The high temperature expansion and exact diagonalization of the N -site fermion model are used to compute the entropy density: our results are consistent with the numerical solution of N =∞ saddle point equations, and the presence of a non-zero entropy density in the limit of vanishing...

We present numerical studies of fermion and boson models with random all-to-all interactions (the SYK models). The high temperature expansion and exact diagonalization of the N -site fermion model are used to compute the entropy density: our results are consistent with the numerical solution of N =1 saddle point equations, and the presence of a non-zero entropy density in the limit of vanishing...

in this paper, the electronic eigenstates and energy spectra of single and two-interacting electrons confined in a concentric double quantum rings with a perpendicular magnetic field in the presence of         on-center donor and acceptor impurities are calculated using the exact diagonalization method. for a single electron case, the binding energy of on-center donor and acceptor impurities ar...