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It has been observed experimentally that the tunneling current across pn tunnel diodes decreases when a magnetic field is applied to it at liquid helium temperatures. Such a decrease is noticed both for longitudinal and transverse applications of magnetic fields relative to the direction of the current flow. Classically, tunneling of particles is regarded to propagate with the speed of light. Therefore, on the basis of the postulates of special theory of relativity tunneling of a potential barrier by particles should be independent of the state of motion of an observer relative to the tunneling system. In other words, the tunneling rate should remain unaffected of the motion of the observer. Therefore, to explain tunneling of particles in a crossed configuration of electric and magnetic fields, a suitable frame of reference for an observer can always be chosen so that the magnetic flux density observed from the new frame reduces to zero. The tunneling along the reduced electric field intensity may then be studied on established laws. The resultant electric field intensity in such a case becomes a function of the original magnetic flux density and it shows a steady decline with the increase in the magnitude of the latter. Therefore, a reduction in the tunneling probability and the tunneling current density is expected when the magnetic flux density normal to the current flow is increased. Finally, at a particular magnetic field intensity the tunneling current density drops to zero. It then turns out that the cyclotron frequency corresponding to this cut off magnetic field is proportional to the reciprocal of the tunneling time derived on the ideas of quantum measurement and observations. Therefore, by recording the normal magnetic flux density required to cut off the tunneling current across pn tunnel diodes immersed in a liquid helium bath, it may be possible to make an estimate of the tunneling time across a potential barrier. The working expression of the calculation of the tunneling time also follows independently of the relativistic treatment outlined above. The identity of results derived on the two approaches seems to justify the fact that the speed Of tunneling is really high enough so that the relativistic treatments may be applied to it as an approximation although tunneling may not propagate with the exact speed of light.
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