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Generation and detection of pure valley current by electrically induced Berry curvature in bilayer graphene

Nature Physics volume 11, pages 1032–1036 (2015)Cite this article

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Abstract

The field of ‘Valleytronics’ has recently been attracting growing interest as a promising concept for the next generation electronics, because non-dissipative pure valley currents with no accompanying net charge flow can be manipulated for computational use, akin to pure spin currents1. Valley is a quantum number defined in an electronic system whose energy bands contain energetically degenerate but non-equivalent local minima (conduction band) or maxima (valence band) due to a certain crystal structure. Specifically, spatial inversion symmetry broken two-dimensional honeycomb lattice systems exhibiting Berry curvature is a subset of possible systems that enable optical2,3,4,5, magnetic6,7,8,9 and electrical control of the valley degree of freedom10,11,12. Here we use dual-gated bilayer graphene to electrically induce and control broken inversion symmetry (or Berry curvature) as well as the carrier density for generating and detecting the pure valley current. In the insulating regime, at zero-magnetic field, we observe a large nonlocal resistance that scales cubically with the local resistivity, which is evidence of pure valley current.

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Figure 1: Scheme for detection of the nonlocal resistance due to valley current flow in BLG.
Figure 2: Measured local and nonlocal resistances RL and RNL.
Figure 3: Temperature dependence of ρmax and RNLmax.
Figure 4: Scaling relation between ρ and RNL at CNP.

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Acknowledgements

We acknowledge fruitful discussion with L. S. Levitov, J. C. W. Song, M. Koshino, M. Ezawa and N. Nagaosa. Y.S. acknowledges support from Japan Society for the Promotion of Science (JSPS) Research Fellowship for Young Scientists and JSPS Program for Leading Graduate Schools (MERIT). M.Y., K.W. and T.T. acknowledge support from JSPS Grant-in-Aid for Scientific Research on Innovative Areas ‘Science of Atomic Layers’. M.Y. acknowledges support from Canon Foundation. I.V.B. acknowledges support from JSPS International Research Fellowship. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan. T.T. acknowledges support from JSPS Grant-in-Aid for Scientific Research A (No. 26248061) and JSPS Innovative Areas ‘Nano Informatics’ (No. 25106006). S.T. acknowledges support from DFG-JST joint research project ‘Topological Electronics’ and JSPS Grant-in-Aid for Scientific Research S (No. 26220710).

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Authors and Affiliations

  1. Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan

    Y. Shimazaki, M. Yamamoto, I. V. Borzenets & S. Tarucha

  2. PRESTO, JST, Kawaguchi-shi, Saitama 332-0012, Japan

    M. Yamamoto

  3. National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0044, Japan

    K. Watanabe & T. Taniguchi

  4. Center for Emergent Matter Science (CEMS), RIKEN, Wako-shi, Saitama 351-0198, Japan

    S. Tarucha

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  1. Y. Shimazaki
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  2. M. Yamamoto
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  4. K. Watanabe
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  6. S. Tarucha
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Contributions

Y.S. conceived the experiment, designed the experiment with M.Y., fabricated the samples, conducted measurements and analysis, interpreted the data with M.Y., and wrote the manuscript with M.Y., I.V.B. and S.T. I.V.B. contributed to the measurements. T.T. and K.W. synthesized h-BN samples. M.Y. and S.T. directed the research. All authors discussed the results and the manuscript.

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Correspondence to M. Yamamoto or S. Tarucha.

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Shimazaki, Y., Yamamoto, M., Borzenets, I. et al. Generation and detection of pure valley current by electrically induced Berry curvature in bilayer graphene. Nature Phys 11, 1032–1036 (2015). https://doi.org/10.1038/nphys3551

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