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arXiv · 1811.02929

Imaging Dirac fermions flow through a circular Veselago lens

Boris Brun·Nicolas Moreau·Sowmya Somanchi·Viet-Hung Nguyen·Kenji Watanabe·Takashi Taniguchi·Jean-Christophe Charlier·Christoph Stampfer·Benoit Hackens
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Abstract

Graphene charge carriers behave as relativistic massless fermions, thereby exhibiting a variety of counter-intuitive behaviors. In particular, at p-n junctions, they behave as photons encountering a negative index media, therefore experiencing a peculiar refraction known as Veselago lensing. However, the way Dirac fermions flow through a Veselago lens remains largely unexplored experimentally. Here, a novel approach to create a movable and tunable circular p-n junction in graphene is proposed, using the polarized tip of a scanning gate microscope. Scanning the tip in the vicinity of a graphene constriction while recording the device conductance yields images related to the electron flow through a circular Veselago lens, revealing a high current density in the lens core, as well as two low current density zones along transport axis. Tight-binding simulations reveal the crucial role of the p-n junction smoothness on these phenomena. The present research adds new dimensions in the control and understanding of Dirac fermions optical elements, a prerequisite to engineer relativistic electron optics devices.

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Boris Brun, Nicolas Moreau, Sowmya Somanchi, Viet-Hung Nguyen, Kenji Watanabe, Takashi Taniguchi, Jean-Christophe Charlier, Christoph Stampfer, Benoit Hackens. 2019-06-19. Imaging Dirac fermions flow through a circular Veselago lens. https://doi.org/10.1103/physrevb.100.041401

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