Tuning of the transmission resonance in Aharonov-Bohm quantum rings

Abstract

We investigate the total transmission probability of a nanoscale Aharonov-Bohm (AB) ring with an embedded quantum dot in one of its arms and a magnetic flux passing through its center. We find a peculiar quantum transport though this system such as a symmetric Breit-Wiper (BW) and an asymmetric Fano transmission resonance. The transition from BW to Fano resonance (or vice verse) occurs by tuning the magnetic AB flux threading through the AB ring, indicating the Fano asymmetric parameter is extended to a complex number. Unique properties of the AB phase coexistent with Fano interference are examined. I. IntroductionRecent advances ,in nanotechnologies have made it possible to fabricate quantum dot structures with gec+ metrical dimensions smaller than the elastic mean free paths. In these nanoscopic systems, electron transport is ballistic and phase coherence can be preserved. Many studies on measurement of the phase of the electron wavefunction have been performed both experimeutally[l]-[4] and theoretically[5]-[10]. Especially, a quantum interference experiment for a quantum dot embedded in an AB ring fabricated in a two-dimensional AlGaAslGaAs heterostructnre was recently performed by Kobayashi et al.[ll]. They studied unique properties of the Fano effect on the phase and coherence of electrons traversing the AB interferometer. This well-known Fano effect[l2], which arises &om the fact that interference between resonant transport through the quantum dot and the direct channel, gives ri& to asymmetric line shapes in the transmission as a function of gate or bias voltage. They also reported in this tunable Fano experiment that an external control, such as a magnetic field, of the relative phase between a discrete level in the QD and the continuum changes the Fano line shapes which is characterized by a complex number of the asymmetric parameter.In this article the total transmission probability of a

Resonance characteristics through double quantum dots embedded in series in an Aharonov–Bohm ring

“…It is noteworthy that the swing from Fano to BW resonance (or vice verse) in a single Fano resonance in the transmission is observed both experimentally and theoretically [1,24]. In addition, the collapse of Fano resonance and anti-resonance in the quantum waveguide with a finite-size attractive impurity is also studied by manipulating the impurity size [25].…”