Aharonov–Bohm effect of quantum Hall edge channels

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Abstract

We fabricated quantum rings by means of local anodic oxidation with an atomic force microscope on GaAs/AlGaAs-heterostructures. In low magnetic fields we observe the Aharonov–Bohm effect of 1D channels in the ring with a period of 60–80 mT, for different devices. By careful tuning the in-plane gate voltages of the ring we also observe Aharonov–Bohm type of oscillations in the quantum Hall regime, with a surprisingly large period when compared to the low field Aharonov–Bohm oscillations.

Introduction

Experimental realization of semiconductor nanostructures opened new ways to study quantum mechanical effects. Ring structures are particularly interesting because they provide a unique system to study quantum interference effects. Due to their small size these structures show very good phase coherence allowing for the observation of, for example, the Aharonov–Bohm effect [1], [2], [3]. In high magnetic fields semiconductors show another important quantum effect, namely the quantum Hall effect [4]. Both phenomena are determined by the same physical constants, h/e in the case of the Aharonov–Bohm effect and h/e2 for the quantum Hall effect. A combination of both effects carries the potential to lead to new and interesting physics [5].

In this research we combine the Aharonov–Bohm effect with the quantum Hall effect in quantum rings created by local anodic oxidation. We observe oscillations of quantum Hall edge channels with a surprisingly large period when compared to the traditional Aharonov–Bohm oscillations observed at low magnetic fields.

Section snippets

Experiment and results

The quantum rings (inset Fig. 1) are fabricated by local anodic oxidation with an atomic force microscope on a GaAs/AlGaAs-heterostructure [6], [7], [8]. A two-dimensional electron gas (2DEG) 40–55 nm below the surface is depleted below oxide lines written on the surface (bright lines in the inset of Fig. 1). The average lithographic diameter of the rings varies from 350 to 300 nm for different devices and they are connected to a source (S) and drain (D) by two quantum point contacts. The

Conclusions

We have fabricated quantum rings by local anodic oxidation with an atomic force microscope in a GaAs/AlGaAs-heterostructure with a 2DEG 40–55 nm below the surface for different devices. The rings show good phase coherence at low temperatures and we have observed the Aharonov–Bohm effect with an oscillation amplitude upto 0.15 e2/h at low magnetic fields. The period of these oscillations, 60 and 80 mT, corresponds nicely with the lithographically defined areas of the two rings.

At high magnetic

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