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Title: Observation of valley Landau-Zener-Bloch oscillations and pseudospin imbalance in photonic graphene
Authors: Sun, Yong
Leykam, Daniel
Nenni, Stephen
Song, Daohong
Chen, Hong
Chong, Yi Dong
Chen, Zhigang
Keywords: DRNTU::Science::Physics
Bloch Oscillation (BO)
Landau-Zener Tunneling (LZT)
Issue Date: 2018
Source: Sun, Y., Leykam, D., Nenni, S., Song, D., Chen, H., Chong, Y. D., et al. (2018). Observation of valley Landau-Zener-Bloch oscillations and pseudospin imbalance in photonic graphene. Physical Review Letters, 121(3), 033904-.
Series/Report no.: Physical Review Letters
Abstract: We demonstrate intervalley Bloch oscillation (BO) and Landau-Zener tunneling (LZT) in an optically induced honeycomb lattice with a refractive-index gradient. Unlike previously observed BO in a gapped square lattice, we show nonadiabatic beam dynamics that are highly sensitive to the direction of the index gradient and the choice of the Dirac cones. In particular, a symmetry-preserving potential leads to nearly perfect LZT and coherent BO between the inequivalent valleys, whereas a symmetry-breaking potential generates asymmetric scattering, imperfect LZT, and valley-sensitive generation of vortices mediated by a pseudospin imbalance. This clearly indicates that, near the Dirac points, the transverse gradient does not always act as a simple scalar force, as commonly assumed, and the LZT probability is strongly affected by the sublattice symmetry as analyzed from an effective Landau-Zener Hamiltonian. Our results illustrate the anisotropic response of an otherwise isotropic Dirac platform to real-space potentials acting as strong driving fields, which may be useful for manipulation of pseudospin and valley degrees of freedom in graphenelike systems.
ISSN: 0031-9007
DOI: 10.1103/PhysRevLett.121.033904
Rights: © 2018 American Physical Society. This paper was published in Physical Review Letters and is made available as an electronic reprint (preprint) with permission of American Physical Society. The published version is available at: []. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.
Fulltext Permission: open
Fulltext Availability: With Fulltext
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