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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Figure 2 a Solid black line: In addition, 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 graphenee carrier density in one of the arms. Wharonov measured resistance is composed of the ring resistance itself and the resistance of the graphene leads.

Received 24 November Published 30 April In diffusive ring-shaped systems, conductance fluctuations can coexist with Aharonov—Bohm oscillations. Also, our measurement temperature is about a factor of 4 higher than the lowest temperatures reported there.

The Deutsche Physikalische Gesellschaft DPG with a tradition extending back to is the largest physical society in the world with more than 61, members. The main advantage of graphene compared to metals for Aharonov—Bohm studies is the reduced screening. Abstract We present low-temperature magnetotransport measurements on graphene rings encapsulated in hexagonal boron nitride.

These oscillations are well explained by taking disorder into account allowing for a coexistence of hard- and soft-wall confinement.

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.

Sign up for new issue notifications. Arrows indicate the direction of the edge channels. We observe that with increasing edge roughness the features of quantization and magnetic focusing weaken until they resemble a shoulder-like structure that graphhene observed in the experiments. Electron beam lithography followed by reactive ion etching is used to define the structure.


Curves are plotted with offsets for clarity. Minima and maxima of the conductance are approximately horizontal and vertical on this plot. It was speculated that this small value might be due to inhomogeneities in the boohm interferometer arms, leading to a tunneling constriction that suppressed the oscillations.

The inset highlights cycloid drift motion of an edge channel along the charge puddle. We investigate the magnetoresistance of a side-gated ring structure etched ahqronov of single-layer graphene.

It has a worldwide membership of around 50 comprising physicists from all sectors, as well as those with an interest in physics. A close up of the 4. zharonov

The width of this peak is significantly smaller than the range of frequencies expected from the range of possible enclosed areas in our geometry indicated as a gray-shaded region in figure 2 c. We also note that the diffusive regime investigated in our device is quite extended in back gate voltage. It supports the sharing of ideas and thoughts within the scientific community, fosters physics teaching and would also like to open a window ahagonov physics for all those with a healthy curiosity.

B 75 Crossref.

B 79 Crossref. For b the background resistance has been subtracted as described in the text.

We therefore speculate that the paths contributing ahaeonov transport, in general, and to the Aharonov—Bohm effect, in particular, may not cover the entire geometric area of the ring arms. Click here to close this aharronov, or press the “Escape” key on your keyboard. B 77 Crossref.

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. The observed data can be interpreted within existing models for ‘dirty metals’.

The inset shows a close-up of the FFT spectrum. For clarity the trace is duplicated with an offset see red arrow. The conductance for the disk is shown for different strength of edge roughness with the result that the position of the conductance minima are rather robust to edge roughness. Rycerz A Act. A smaller radius will lead to a larger oscillation amplitude, which may explain the improved amplitude in our measurements. Buy this article in print.

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[] The Aharonov-Bohm effect in graphene rings

The Ahaonov wavelength corresponding to the carrier density mentioned above is. A magnetic field is applied perpendicular to the sample plane. Since then, amazing progress in the fabrication graphenf increasingly more complex nanostructures has been made. Note that in order for interference to happen at all, part of the wave function has to leak to the reflecting edge channel as otherwise unitarity ensures perfect transmission. Red box indicates the selected B -field region.

Condensed Matter > Mesoscale and Nanoscale Physics

The lower panel shows the semiclassically calculated transmission through the ring for more details see text. Zoom In Zoom Out Reset image size. The exponential term on the right-hand side contains the radius of the ring r 0. In panel c the traces are plotted with an offset for clarity. Bachtold A et al Nature Crossref. 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.

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

B 80 Crossref. The density change is related via a parallel plate capacitor model to a change in back gate voltage, i. To find out more, see our Privacy and Cookies policy. Inset shows larger measurement range. It therefore remains unclear to us how the concept of graphnee Thouless energy as an energy scale for wave function correlations can be transferred to the graphene system.