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.
|Country:||Antigua & Barbuda|
|Published (Last):||12 September 2015|
|PDF File Size:||3.59 Mb|
|ePub File Size:||20.22 Mb|
|Price:||Free* [*Free Regsitration Required]|
The observed data can be interpreted within existing models for ‘dirty metals’.
The inset shows a close-up of the Graaphene spectrum. Standard low-frequency lock-in techniques are used to measure the resistance by applying a constant current. Zoom In Zoom Out Reset image size. Click here to close this overlay, or press the “Escape” key on your keyboard.
It was speculated that this small value might be due to inhomogeneities in the two interferometer arms, leading to a tunneling constriction that suppressed the oscillations. A magnetic field is applied perpendicular to the sample plane. Electron beam lithography followed by reactive ion etching is used to define the structure. Its publishing company, IOP Publishing, is a world leader boym professional scientific communications.
Inset illustrates the trajectory of charge carriers inside a conductance plateau. 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. 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. For comparison, at the same density, the mean free path is. However, trying to relate the visibilities observed in the two experiments quantitatively assuming that all experimental parameters except the ring radius are the same would lead to a phase-coherence length l smaller than the ring circumference L and only slightly larger than the ring radius r 0.
We perform tight-binding calculations which allow us to reproduce all significant features of our experimental findings and enable a deeper understanding of bphm underlying physics. The measured resistance is composed of the ring resistance itself and the resistance sharonov the graphene leads.
The Aharonov–Bohm effect in a side-gated graphene ring – IOPscience
This makes it possible to use external gates for locally tuning the density and the Fermi wave vector in one of ahharonov arms and therefore allows us to observe the electrostatic Aharonov—Bohm effect without the use of tunnel barriers in the arms of the ring. For b the background resistance has been subtracted as described in the text.
The data are analyzed by a simple dirty metal model justified by a comparison of the different length scales characterizing the system. 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.
B 80 Crossref. We therefore speculate that the paths contributing to transport, in general, and to the Aharonov—Bohm effect, in particular, may not cover the entire geometric area of the ring arms. 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 Fermi wavelength corresponding to the carrier density mentioned above is. The only relevant effect of the magnetic field on the charge carrier dynamics is therefore caused by the field-induced Aharonov—Bohm phase.
Arrows indicate the direction of the edge channels. For more information see text. Therefore measurements presented here were taken over only small ranges of back gate voltage after having allowed the sample to stabilize in this range.
One possible interpretation is that the sample has rough unordered edges leading to a region along the edges that does not contribute to the electrical transport.
The Aharonov–Bohm effect in a side-gated graphene ring
It works to advance physics research, application and education; and engages with policy makers and the public to develop awareness and understanding aharojov physics.
To find out more, see our Privacy and Cookies policy. On the other hand, the electric field may change the electron density and thereby the Fermi wavelength of the carriers.
The solid green line is the line of constant energy along which Fig. The geometrical aspect ratio is roughly one-third of this aspect ratio estimated from the sample resistance bohmm the charge neutrality point.
The exponential term on the right-hand side contains the radius of the ring r 0. Abstract We present low-temperature magnetotransport measurements on graphene rings encapsulated in hexagonal boron nitride. Clear periodic oscillations can be seen on top of this background.
B 96— Published 3 November