arXiv subjects

U. Eckern

Publications and source records attributed to U. Eckern.

40 records · Page 3Linked to original sources

arXiv1997

Anderson-localization versus delocalization of interacting fermions in one dimension

Using the density matrix renormalization group algorithm, we investigate the lattice model for spinless fermions in one dimension in the presence of a strong interaction and disorder. The phase sensitivity of the ground state energy is determined with high accuracy for systems up to a size of 60 lattice constants. This quantity is found to be log-normally distributed. The fluctuations grow algebraically with system size with a universal exponent of ~2/3 in the localized region of the phase diagram. Surprizingly, we find, for an attractive interaction, a delocalized phase of finite extension. The boundary of this delocalized phase is determined.

cond-mat.str-el↗

arXiv1997

Persistent current induced by magnetic impurities

We calculate the average persistent current in a normal conducting, mesoscopic ring in the diffusive regime. In the presence of magnetic impurities, a contribution to the persistent current is identified, which is related to fluctuations in the electron spin density. Assuming a spin-flip scattering rate which is comparable to the Thouless energy E_c and low temperature, this new contribution to the persistent current is of the order $I\sim E_c^2/(kTϕ_0)$, which is considerably larger than the persistent current induced by the electron-electron interaction.

cond-mat.mes-hall↗

arXiv1996

Phase Coherence in a Random One-Dimensional System of Interacting Fermions: A Density Matrix Renormalization Group Study

Using the density matrix renormalization group algorithm, we study the model of spinless fermions with nearest-neighbor interaction on a ring in the presence of disorder. We determine the spatial decay of the density induced by a defect (Friedel oscillations), and the phase sensitivity of the ground state energy $\DE= (-)^{N} (E(ϕ=0) - E(ϕ=π))$, where $ϕ= 2πΦ/Φ_0$ ($N$ is the number of fermions, $Φ$ the magnetic flux, and $Φ_0=h/e$ the flux quantum), for a disordered system versus the system size $M$. The quantity $\ln{(M \DE)}$ is found to have a normal distribution to a good approximation. The ``localization length'' decreases (increases) for a repulsive (attractive) interaction.

cond-mat↗

arXiv1995

Quantum Coherence in an Exactly Solvable One-dimensional Model with Defects

Using the Quantum Inverse Scattering Method we construct an integrable Heisenberg-XXZ-model, or equivalently a model for spinless fermions with nearest-neighbour interaction, with defects. Each defect involves three sites with a fine tuning between nearest-neighbour and next-nearest-neighbour terms. We investigate the finite size corrections to the ground state energy and its dependence on an external flux as a function of a parameter $ν$, characterizing the strength of the defects. For intermediate values of $ν$, both quantities become very small, although the ground state wavefunction remains extended.

cond-mat↗