Bouncing transient currents and SQUID-like voltage in nano devices at half filling

Nanorings asymmetrically connected to wires show different kinds of quantum interference phenomena under sudden excitations and in steady current conditions. Here, we contrast the transient current caused by an abrupt bias to the magnetic effects at constant current. A repulsive impurity can cause charge buildup in one of the arms and reverse current spikes. Moreover, it can cause transitions from laminar current flow to vortices, and also change the chirality of the vortex. The magnetic behavior of these devices is also very peculiar. Those nanocircuits, that consist of an odd number of atoms, behave in a fundamentally different manner compared to those that consist of an even number of atoms. The circuits having an odd number of sites connected to long-enough symmetric wires are diamagnetic; they display half-fluxon periodicity induced by many-body symmetry even in the absence of electron-phonon and electron-electron interactions. In principle, one can operate a kind of quantum interference device without superconductors. Since there is no gap and no critical temperature, one predicts qualitatively the same behavior at and above room temperature, although with a reduced current. The circuits with even site numbers, on the other hand, are paramagnetic.