Gate-tunable Veselago Interference in a Bipolar Graphene Microcavity*

We present a novel device architecture of a graphene microcavity defined by carefully engineered local strain and electrostatic fields. We create a controlled electron-optic interference process at zero magnetic fields as a result of consecutive Veselago refractions in the microcavity and provide direct experimental evidence through low-temperature electrical transport measurements. The experimentally observed first-, second-, and third-order interference peaks agree quantitatively with the Veselago physics in a microcavity. In addition, we demonstrate decoherence of the interference by an external magnetic field, as the cyclotron radius becomes comparable to the interference length scale. For its application in electron-optics, we use Veselago interference to localize uncollimated electrons and characterize its contribution in further improving collimation efficiency in graphene pn-junctions [1-2]. Our work sheds new light on relativistic single-particle physics and provides important technical improvements toward next-generation quantum devices based on the coherent manipulation of electron momentum and trajectory.

[1] Chen, S. et al. Science 353, 1522–1525 (2016).

[2] Wang, K. et al. PNAS USA 116, 6575–6579 (2019)