We investigate phase-coherent transport and show Aharonov-Bohm (AB) oscillations in quasiballistic graphene rings with hard confinement. Aharonov-Bohm oscillations are observed in a graphene quantum ring with a topgate covering one arm of the ring. As graphene is a gapless semiconductor, this. Graphene rings in magnetic fields: Aharonov–Bohm effect and valley splitting. J Wurm1,2, M Wimmer1, H U Baranger2 and K Richter1. Published 3 February.

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Grapnene dashed lines shows G 2 W used for background subtraction. We therefore believe that the smaller ring dimensions in combination with the four-terminal arrangement may be responsible for the larger value of the visibility observed in our experiment. The inset shows a close-up of the FFT spectrum. In aharonv, our graphene ring has better tunability as it is equipped not only with a back gate, which allows us to change the charge carrier density in the complete sample, but also with side gates, allowing a local tuning of the charge carrier density in one of the arms.

Figure 6 a Schematic illustration of a ring with a charge puddle connecting the inner and outer edge channel in the quantum Hall regime. Solid lines highlight constant cyclotron radii for selected values. Inset illustrates the trajectory of charge carriers inside a conductance plateau. B 80 Crossref. In previous studies on metal rings, the effect of electric fields on ahaornov Aharonov—Bohm oscillations has been investigated, and two possible scenarios were discussed: Values are normalized with respect to the conductance at zero B field and an offset is added gaphene clarity.

The observations are in good agreement with an interpretation in terms of diffusive metallic transport in a ring geometry.

Condensed Matter > Mesoscale and Nanoscale Physics

The amplitude of the Aharonov—Bohm oscillations is modulated as a function of magnetic field on the same scale as the background resistance, indicating that a finite number of paths enclosing a range of different areas contribute to the oscillations. We remark here that this assumption, and the reasoning based on it as given in the main text, corresponds to the usual argument made for dirty metals.


Since then, amazing progress in the fabrication of increasingly more complex nanostructures has been made. It works to advance physics research, application and education; and engages with policy makers and the public to develop awareness and understanding of physics. The solid green line is the line of constant energy along which Fig.

B 76 Crossref.

Closer inspection shows that the antisymmetric part in the magnetic field of each trace not shown is more than a factor of 10 smaller than the symmetric part.

The lower agaronov shows the semiclassically calculated transmission through the ring for more details see text.

For b the background resistance has been subtracted as described in the text. By continuing to use this site you agree to our use of cookies.

Moreover we show signatures of magnetic focusing effects at small magnetic fields confirming ballistic transport. The density change is related via a parallel plate capacitor model to a change in back gate voltage, i. The main advantage of graphene compared to metals for Aharonov—Bohm studies is the reduced screening.

In panel c the traces are plotted with an offset for clarity.

[] The Aharonov-Bohm effect in graphene rings

A Crossref. Oxford University Press p The observed data can be interpreted within existing models for ‘dirty metals’.

It has a worldwide membership of around 50 comprising physicists from all sectors, as well as those with an interest in physics. The red trace in the inset corresponds to the gtaphene and vertically offset negative B -field branch.

The B -field axis is divided into three regimes: The Fermi wavelength corresponding to the carrier density mentioned above is. Electron beam lithography followed by reactive ion etching is used to define the structure.


In a semiclassical Drude picture, these resistances can be calculated from the geometric aspect ratios i. However, due to limited sample stability, the visibility of the oscillations at a given back gate voltage depends on the back gate voltage history.

We discuss the latter effect in more detail below, since the relative change in the Fermi wavelength is expected to be more pronounced in graphene compared to conventional metals.

For comparison, at the same density, the mean free path is. Abstract We present low-temperature magnetotransport measurements on graphene rings encapsulated in hexagonal boron nitride.

Curves are plotted with offsets for clarity. It supports the sharing of ideas and thoughts within the scientific community, fosters physics teaching and would also like to open a window bihm physics for all those with a healthy curiosity. Bachtold A et al Nature Crossref. B 40 Crossref.

Inset shows larger measurement range. Therefore, the presented measurements are all close to the diffusive dirty metal regime, and carrier scattering at the sample boundaries alone cannot fully account for the value of the mean free path. For more information bkhm text. We perform tight-binding calculations which allow us to reproduce all significant features of our experimental findings and enable a deeper understanding of the underlying physics.

Zoom In Zoom Out Reset image size. It therefore remains unclear to us how the concept of the Thouless energy as an energy scale for wave function correlations can be transferred to the graphene system.

The data are analyzed by a simple dirty metal model justified by a comparison of the different length scales characterizing the system.