The Momentum Distribution and Van Hove Function in Low Density Quantum Systems.

Kyoji Nishikawa

Using Feynman diagrams, the dissipative hehaviour of a large quantum system of many fermions is discussed. On the basis of linked cluster expansion of the time-dependent perturbation theory, the master equation is derived for the time sufficiently long compared to the effective collision time and for a slowly varying initial distribution in the momentum space. Van Hove's result for weak coupling limit and the equation for low density limit are obtained as special cases.

Benjamin Withers, H. R. Glyde

Pui-Man Lam

Thomas Husslein, D. M. Newns, Hans-Georg Mattutis +5 more

We present calculations of the tt'-Hubbard model using Quantum Monte Carlo techniques. The parameters are chosen so that the van Hove Singularity in the density of states and the Fermi level coincide. We study the behaviour of the system with increasing Hubbard interaction U. Special emphasis is on the spin-spin correlation (SSC). Unusual behaviour for large U is observed there and in the momentum distribution function ( n(q)).

Roderick I. Sutherland

Thomas Husslein, D. M. Newns, H. G. Mattutis +5 more

We present calculations of the tt'-Hubbard model using Quantum Monte Carlo techniques. The parameters are chosen so that the van Hove Singularity in the density of states and the Fermi level coincide. We study the behaviour of the system with increasing Hubbard interaction U. Special emphasis is on the spin-spin correlation (SSC). Unusual behaviour for large U is observed there and in the momentum distribution function (n(q)).