Localized states in a semiconductor quantum ring with a tangent wire

TL;DR

This paper investigates localized states in a semiconductor quantum ring with a tangent wire, revealing how geometric and magnetic parameters influence Fano interference, antiresonance gaps, and transmission properties, with potential applications in quantum devices.

Contribution

It extends localized state analysis to a ring geometry with tangent connection, exploring the effects on Fano interference and transmission modulation, demonstrating robustness for practical use.

Findings

Localized state trapped at the intersection with energy inside the lowest subband.

Fano dip diminishes as the ring's inner radius increases.

An antiresonance gap can be modulated by magnetic flux.

Abstract

We extend a special kind of localized state trapped at the intersection due to the geometric confinement, first proposed in a three-terminal-opening T-shaped structure [Euro. Phys. Lett. {\bf 55}, 539 (2001)], into a ring geometry with a tangent connection to the wire. In this ring geometry, there exists one localized state trapped at the intersection with energy lying inside the lowest subband. We systematically study this localized state and the resulting Fano-type interference due to the coupling between this localized state and the continuum ones. It is found that the increase of the inner radius of ring weakens the coupling to the continuum ones and the asymmetric Fano dip fades away. A wide energy gap in transmission appears due to the interplay of two types of antiresonances: the Fano-type antiresonance and the structure antiresonance. The size of this antiresonance gap can be modulated by adjusting the magnetic flux. Moreover, a large transmission amplitude can be obtained in the same gap area. The strong robustness of the antiresonance gap is demonstrated showing the feasibility of the proposed geometry for a real application.