TOPOLOGICAL TRANSITIONS IN BERRYS PHASE INTERFERENCE EFFECTS

We consider a topological transition which is an abrupt variation from pi to zero of Berry's phase, in the case when it is a phase difference of interfering waves. It manifests itself in a steplike current-magnetic field and current-gate voltage characteristics predicted for in-plane magnetoresistance of rings in noncentrosymmetric materials. Transition points occur at external magnetic fields equal to momentum-dependent effective magnetic fields for different tunneling channels of a quasi-one-dimensional ring. Similar effects due to the angular anisotropy of electron g factor are considered.