We study magnetic traps with very high trap frequencies where the spin is coupled to motion of atom. This allows us investigate how Born–Oppenheimer approximation fails and effective electric fields appear as consequence non-adiabatic dynamics. The results are based on exact numerical diagonalization full Hamiltonian describing coupling between internal external degrees freedom. position in ene...

We investigate the one-dimensional quantum XXZ model in the presence of diagonal disorder. Recently the model has been analyzed with the help of field-theoretical renormalization group methods, and a phase diagram has been predicted. We study the model with exact diagonalization techniques up to chain lengths of 16 sites. Using finite-size scaling methods we estimate critical exponents and the ...

Motivated bymagnetization studies of the “telephon number compound” Sr14Cu24O41 we investigate doped Heisenberg spin rings by means of complete numerical diagonalization of a Heisenberg Hamiltonian that depends parametrically on hole positions. A comparison with experimental magnetization data reveals rather accurate information about the screened electrostatic interaction between the charged h...

We present a modified Lanczos algorithm to diagonalize lattice Hamiltonians with dramatically reduced memory requirements, without restricting to variational ansatzes. The lattice of size N is partitioned into two subclusters. At each iteration the Lanczos vector is projected into two sets of n(svd) smaller subcluster vectors using singular value decomposition. For low entanglement entropy S(ee...

We investigate ground state properties of a quasi-one-dimensional electron-lattice coupled model for quarter-filled molecular conductors. The effective one-dimensional extended Hubbard model coupled to adiabatic lattice degree of freedom is derived by the inter-chain mean-field approximation and solved by Lanczos exact diagonalization method. We find that the critical behavior among lattice tet...

An efficient method of computing magnetic exchange interactions in systems with strong correlations is introduced. It is based on a magnetic force theorem that evaluates linear response due to rotations of magnetic moments and uses a generalized spectral density functional framework allowing us to explore several approximations ranging from local density functional to exact diagonalization base...

The zero–temperature conductance of diatomic molecule, modelled as a correlated double quantum dot attached to noninteracting leads is investigated. We utilize the Rejec–Ramšak formulas, relating the linear–response conductance to the ground–state energy dependence on magnetic flux within the framework of EDABI method, which combines exact diagonalization with ab initio calculations. The single...

Skyrmions in the FQHE at filling fractions above ν = 1/3 are studied within the anyon model and by exact diagonalization. Relations to the composite fermion theory are pointed out. We find that unpolarized quasiparticles above ν = 1/3 are stable below B ≈ 0.02T . At low Zeeman energy the polarization in the range ν = 8/5 . . . 5/3 is found to be a linear function of the filling factor. We also ...

Ground state of the bond-random antiferromagnetic S = 1 Heisenberg chain with the biquadratic interaction −β ∑ i(Si · Si+1) 2 is investigated by means of the exact-diagonalization method and the finite-size-scaling analysis. It is shown that the Haldane phase β ≈ 0 persists against the randomness; namely, no randomness-driven phase transition is observed until at a point of extremelybroad-bond ...