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.
|Published (Last):||24 June 2015|
|PDF File Size:||11.87 Mb|
|ePub File Size:||9.13 Mb|
|Price:||Free* [*Free Regsitration Required]|
There was a problem providing the content you requested
We present low-temperature magnetotransport measurements on graphene rings encapsulated in hexagonal boron nitride. We investigate phase-coherent transport and show Aharonov-Bohm AB oscillations in quasiballistic graphene rings with hard confinement. Moreover we show signatures of magnetic focusing effects at small magnetic fields confirming ballistic transport.
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.
Finally, we report on the observation of the AB conductance oscillations in the quantum Hall regime at reasonable high magnetic fields, where we find regions with enhanced AB oscillation visibility with values up to 0. These oscillations are well explained by taking disorder into account allowing for a coexistence of hard- and soft-wall confinement.
The B -field axis is divided into three regimes: Red dashed graphsne shows G 2 W used for background subtraction. For clarity the trace bhm duplicated with an offset see red arrow. In panel c the traces are plotted with an offset for clarity.
Frequency range of individual AB oscillation modes marked by arrows.
Horizontal lines indicate frequencies for inner, mean, and outer radii as illustrated in the inset. Values are normalized with respect to the conductance at zero B field and an offset is added for clarity. Solid lines highlight garphene cyclotron radii for selected values.
Curves are plotted with offsets for clarity. A close up of the 4. The red trace in the inset corresponds to the mirrored and vertically offset negative B -field branch. Vertical dashed lines again represent cyclotron radii as depicted in panel d. Inset illustrates the trajectory of charge carriers inside a conductance plateau. Inset shows larger measurement aaronov.
The Aharonov–Bohm effect in a side-gated graphene ring – IOPscience
Red box indicates the selected B -field region. Arrows indicate the direction of the edge channels. The aharoonov highlights cycloid drift motion of an edge channel along the charge puddle.
This interference can be tuned via the AB phase of the area green and red encircled. 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.
The inset vohm a close-up of the FFT spectrum. For more information see text. Minima and maxima of the conductance are approximately horizontal and vertical on this plot.
The solid green line is the line of constant energy along which Fig. The lower panel shows the semiclassically calculated transmission through the ring for more details see text. We observe that the trajectory of the electron starting in the left lead performs a skipping orbit which after four reflections at the boundary enters the right lead.
Note that sharonov results also approximately match the results of Fig. The conductance for the disk is shown for different strength of edge fraphene with the result that the position of the conductance minima are rather robust to edge roughness.
We observe that with increasing edge roughness the features of quantization and magnetic focusing weaken until they resemble a shoulder-like structure that was observed in the experiments. B 96— Published 3 November Abstract We present low-temperature magnetotransport measurements on graphene rings encapsulated in hexagonal boron nitride. Weyl fermions are observed in a solid. Figure 1 a Scanning force microscopy image of device 1 with a schematic of the measurement configuration.
Figure 2 a Solid black line: Figure 4 a Schematic representation of the different ring geometries of samples 1 and 2.
 The Aharonov-Bohm effect in graphene rings
Figure 6 a Schematic illustration of a ring with a charge puddle connecting the inner and outer edge channel in the quantum Hall regime. Sign up to receive regular email alerts from Physical Review B. Series I Physics Physique Fizika.