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

TL;DR

This paper investigates quantum interference phenomena in nano-circuits with asymmetric connections, revealing unique transient and magnetic behaviors depending on atom count, and proposes a new type of quantum interference device operable at room temperature.

Contribution

It demonstrates how odd and even atom-number nano-circuits exhibit fundamentally different magnetic and current behaviors, introducing a potential room-temperature quantum interference device without superconductors.

Findings

Odd-site circuits are diamagnetic with half-fluxon periodicity.

Even-site circuits are paramagnetic.

Charge build-up and vortex transitions occur due to impurities.

Abstract

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 build-up 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 nano-circuits which consist of an odd number of atoms behave in a fundamentally different manner compared to those which 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 new 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.