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Quantum interference and Klein tunnelling in graphene heterojunctions

Nature Physics volume 5, pages 222–226 (2009)Cite this article

Abstract

The observation of quantum conductance oscillations in mesoscopic systems has traditionally required the confinement of the carriers to a phase space of reduced dimensionality1,2,3,4. Although electron optics such as lensing5 and focusing6 have been demonstrated experimentally, building a collimated electron interferometer in two unconfined dimensions has remained a challenge owing to the difficulty of creating electrostatic barriers that are sharp on the order of the electron wavelength7. Here, we report the observation of conductance oscillations in extremely narrow graphene heterostructures where a resonant cavity is formed between two electrostatically created bipolar junctions. Analysis of the oscillations confirms that p–n junctions have a collimating effect on ballistically transmitted carriers8. The phase shift observed in the conductance fringes at low magnetic fields is a signature of the perfect transmission of carriers normally incident on the junctions9 and thus constitutes a direct experimental observation of ‘Klein tunnelling’10,11,12.

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Figure 1: Graphene heterojunction device schematic diagrams and conductance measurements.
Figure 2: Density and magnetic-field dependence of the oscillatory conductance; origin of the Klein tunnelling phase shift.
Figure 3: Comparison of experimental data to the theoretical model, and temperature dependence.

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Acknowledgements

The authors would like to thank I. L. Aleiner, K. I. Bolotin, M. Y. Han, E. A. Henriksen, L. S. Levitov and H. L. Stormer for discussions, and I. Meric and M. Y. Han for help with sample preparation. This work is supported by the ONR (No. N000150610138), FENA, NRI, NSEC (No. CHE-0117752) and NYSTAR. Sample preparation was supported by the DOE (DE-FG02-05ER46215).

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  1. Department of Physics, Columbia University, New York 10027, USA

    Andrea F. Young & Philip Kim

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  1. Andrea F. Young
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  2. Philip Kim
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Correspondence to Philip Kim.

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Young, A., Kim, P. Quantum interference and Klein tunnelling in graphene heterojunctions. Nature Phys 5, 222–226 (2009). https://doi.org/10.1038/nphys1198

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