Weak–coupling calculation of the gap structure of doped n–leg Hubbard ladders Abstract In weak coupling, the spin gap in doped, even, n–leg periodic Hubbard ladders reflects the energy to break a pair into separate quasiparticles. Here we investigate the structure of the gap within a spin–fluctuation exchange approximation. We also calculate the amplitude for removing a singlet pair from two la...

The spin densities of the nitroxides H 2 N O , (CH 3 )HNO and (CH 3 ) 2 NO have been studied by iterative CI methods. Calculations at different geometries with various basis sets were performed. It is found that the spin distribution is delocalized within the N O group, and substitution of the hydrogen atoms on the nitroxyl group by methyl groups changes the spin distribution significantly. Ele...

Common ground to recent studies exploiting relations between dynamical systems and non-equilibrium statistical mechanics is, so we argue, the standard Gibbs formalism applied on the level of space-time histories. The assumptions (chaoticity principle) underlying the Gallavotti-Cohen fluctuation theorem make it possible, using symbolic dynamics, to employ the theory of one-dimensional lattice sp...

The response function of domain growth processes, and in particular the violation of the fluctuation-dissipation theorem, are studied both analytically and numerically. In the asymptotic limit of large times, the fluctuation-dissipation ratio X, which quantifies this violation, tends to one if C > m and to zero if C < m, corresponding to the fast (“bulk”) and slow (“domain-wall”) responses, res...

We investigate theoretically the Seebeck effect in materials close to a ferromagnetic quantum critical point to explain anomalous behaviour at low temperatures. It is found that the main effect of spin fluctuations is to enhance the coefficient of the leading T-linear term, and a quantum critical behaviour characterized by a spin-fluctuation temperature appears in the temperature dependence of ...

We significantly reduce the critical current Ic0 for the onset of spin torque switching of the free layer in nanometer-scale in-plane magnetized spin valves by partially canceling its demagnetization field (Hd) through the utilization of Co/Ni multilayer free layers. A zero-thermal-fluctuation critical current density Jc0 ~ 2 × 106 A/cm2 is determined through both current ramp rate and nanoseco...