3 research outputs found
Nonlinear ac conductivity of one-dimensional Mott insulators
We discuss a semiclassical calculation of low energy charge transport in
one-dimensional (1d) insulators with a focus on Mott insulators, whose charge
degrees of freedom are gapped due to the combination of short range
interactions and a periodic lattice potential. Combining RG and instanton
methods, we calculate the nonlinear ac conductivity and interpret the result in
terms of multi-photon absorption. We compare the result of the semiclassical
calculation for interacting systems to a perturbative, fully quantum mechanical
calculation of multi-photon absorption in a 1d band insulator and find good
agreement when the number of simultaneously absorbed photons is large.Comment: Dedicated to Thomas Nattermann on the occasion of his 60th birthday.
To appear in JSTAT. 5 pages, 2 figure
Stability of fluxon motion in long Josephson junctions at high bias
In long Josephson junctions the motion of fluxons is revealed by the existence of current steps, zero-field steps, in the current-voltage characteristics. In this paper we investigate the stability of the fluxon motion when high values of the current bias are involved. The investigation is carried on by numerical integration of the model equation, the perturbed sine-Gordon equation, simulating junctions of overlap and annular geometry. A detailed description of the mechanism for the switching from the top of the zero-field step for both geometries is reported. Moreover, the effect of the various dissipations and of the junction length on the switching-current value is investigated. A simple boundary model is able to describe, for junctions of overlap geometry, the qualitative dependence of the switching current on the system parameters