Influence of a variable magnetic field on interference of electron beams: Aharonov-Bohm effect

A. N. Ageev, Sergei Yu. Davydov

王瑞峰

Muslim Juliasih Partini

ABSTRACT\nThe interaction of charged and uncharged particles with intrinsic magnetic moment for the latter with an electromagnetic field in the microworld brings out the actual role of the electromagnetic potentials as emphasized in quantum theory which generate electromagnetic interaction via gauge invariance requirement.\nIn the Aharonov-Bohm (A-B) effect (dealing with two electron coherent beams passing a double slit system), the resulting interference pattern is shifted by the insertion of a very long solenoid between the two electron beams with an influence described by the magnetic vector\npotential A on the electron wave functions. Aharonov and Casher presented the complement of the Aharonov-Bohm effect involving the role of the electric scalar potential co on a beam of neutrons each carrying an internal magnetic dipole moment. A similar shift in the interference pattern is found involving two coherent neutron beam interference, where the solenoid in the A-B arrangement is replaced by an electric line charge, and the electrons by polarized neutrons. The effective Hamiltonian describing the two effects is used to determine the interference pattern.\nThe experiment to verify the existence of the Aharonov-Bohm effect which have been performed using an electron holography with a small toroidal ferromagnetic substance confining a magnetic flux by Tonomura in 1982 is discussed. The Aharonov-Casher effect, which was conducted using a Bonse-Hart single-crystal neutron interferometer by A. Cirnmino in 1989, is also discussed. Both experimental results lead to the same phenomenon: a phase shift in the observed pattern interference quantitatively explained as caused by the influence of the proper component of the electrodynamic potentials.\n\nKey Word: Kuantum, Aharonov- cahser

Sergei Yu. Davydov, A. N. Ageev

It is shown that the phase and frequency modulation of the vector potential responsible for the Aharonov-Bohm effect causes changes in the interference pattern that may be used to study this effect under conditions of an ac magnetic flux.

Akira Tonomura

G. R. Freeman, Larry D. Coulson, Norman Henry March

When an electron beam passes outside a confined magnetic flux, the motional magnetic field of the electrons overlaps the confined flux. The potential energy of the magnetic dipolar interaction of the motional magnetic field with the confined magnetic flux causes the velocity of the electrons to change slightly, which shifts the phase of the electron de Broglie wave. When portions of an electron beam pass on different sides of a confined flux and are then mixed, they produce an interference pattern. There is a similar magnetic dipolar interaction, with resulting velocity and phase changes, when a beam of magnetic particles interacts with the motional magnetic flux produced by their crossing a strong electric field. These are classical electromagnetic dipolar (not Lorentz) interactions that causes changes in Berry's geometrical phase, but are not ESAB or AC effects. Data that were suggested to demonstrate the ESAB and AC effects have been quantitatively interpreted in terms of motional magnetic fields and velocity changes.