Aharonov-Bohm Effects and the Topology of Electromagnetic Fields in Spacetime

We propose a novel Aharonov-Bohm (AB) scheme where a nonzero AB phase difference appears even if the interferometer paths do not enclose a magnetic flux. In the proposal, the current in a solenoid outside the interferometer varies in time while the quantum particle is in a superposition state inside two Faraday cages, such that it is always subjected to null electromagnetic fields. At first glance, this result could challenge the topological nature of the AB effect. However, we generalize the effect analysis by considering the topology of the electromagnetic fields and particles trajectories in spacetime, demonstrating the topological nature of this novel situation and also of the electric AB effect. The experimental implementation of the proposed scheme in principle is feasible with current technology.