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Tunneling in a normal tunnel junction depends crucially on the
electromangetic environment that the tunneling electron feels.
We have investigated asymptotic behavior of normal tunnel junctions at
voltages where even the best ohmic environments start to look like RC
transmission lines. In the experiments, this is manifested by an exceedingly
slow approach to the linear behavior above the Coulomb gap. As expected on
the basis of P(E)-theory, better fits are obtained using 1/sqrt(V)- than
1/V-dependence for the asymptote. These results agree with the horizon
picture if the frequency-dependent phase velocity is employed instead of the
speed of light in order to determine the extent of the surroundings seen by
the junction
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 Reduced
current vs. voltage for a sample with tunneling resistance 11.1 kOhms in an
environment modelled by RC-transmission line |
