14 research outputs found
Non-Linear I-V Characteristics of Double Schottky Barriers and Polycrystalline Semiconductors
An attempt to determine theoretically the highly non-linear current-voltage
(I-V) characteristics of polycrystalline semiconductors, such as ZnO-based
varistors, is made from the electrical properties of individual grain
boundaries under dc bias. The role played by the fluctuations of double
Schottky barrier heights at grain interfaces on driving electrical breakdown
phenomena of macroscopic samples is pointed out in terms of a binary mixture
model. An alternative trial form for the double Schottky barrier height is
introduced to reproduce the breakdown voltage as well as the high non-linear
coefficient alpha, where I propto V^{alpha}. -------------
Copies upon request to: [email protected]: CM-ICTP/92/1
Production efficiency of Feshbach molecules in fermion systems
We present a consistent nonequilibrium theory for the production of molecular
dimers from a two-component quantum-degenerate fermion atomic gas, via a linear
downward sweep of the magnetic field across a Feshbach resonance. This problem
raises interest because it is presently unclear as to why deviations from the
universal Landau-Zener formula for the transition probability at two-level
crossing are observed in the experimentally measured production efficiencies.
We show that the molecular conversion efficiency is represented by a power
series in terms of a dimensionless parameter which, in the zero-temperature
limit, depends solely on the initial gas density and the Landau-Zener
parameter. Our result reveals a hindrance of the canonical Landau-Zener
transition probability due to many-body effects, and presents an explanation
for the experimentally observed deviations [K.E. Strecker \textit{et al.},
Phys. Rev. Lett. {\bf 91}, 080406 (2003)].Comment: 4 pages, 1 figur