Breakdown of `phase rigidity' and variations of the Fano effect in closed Aharonov-Bohm interferometers

TL;DR

This paper explains the apparent breakdown of phase rigidity in closed Aharonov-Bohm interferometers by modeling multiple electronic paths, showing how conductance maxima shift with magnetic flux and gate voltage.

Contribution

It introduces a simple model accounting for multiple paths around the ring, explaining experimental deviations from expected periodic conductance behavior.

Findings

Conductance maxima shift with magnetic flux and gate voltage.

Multiple paths cause apparent phase rigidity breakdown.

Model fits experimental Coulomb blockade data.

Abstract

Although the conductance of a closed Aharonov-Bohm interferometer, with a quantum dot on one branch, obeys the Onsager symmetry under magnetic field reversal, it needs not be a periodic function of this field: the conductance maxima move with both the field and the gate voltage on the dot, in an apparent breakdown of `phase rigidity'. These experimental findings are explained theoretically as resulting from multiple electronic paths around the interferometer ring. Data containing several Coulomb blockade peaks, whose shapes change with the magnetic flux, are fitted to a simple model, in which each resonant level on the dot couples to a different path around the ring.