Nonreciprocity and one-way propagation of optical signals are crucial for modern nanophotonic technology, and typically achieved using magneto-optical effects requiring large magnetic biases. Here we suggest a fundamentally novel approach to achieve unidirectional propagation of surface plasmon-polaritons (SPPs) at metal-dielectric interfaces. We employ a direct electric current in metals, which produces a Doppler frequency shift of SPPs due to the uniform drift of electrons. This tilts the SPP dispersion, enabling one-way propagation, as well as zero and negative group velocities. The results are demonstrated for planar interfaces and cylindrical nanowire waveguides.RIKEN iTHES Project, MURI Center for Dynamic Magneto-Optics, Air Force Office of Scientific Research (AFOSR) (FA9550-14-1-0040); the IMPACT program
of JST, Japan Society for the Promotion of Science (JSPS) (KAKENHI); Core Research for Evolutional Science and Technology (CREST) (JPMJCR1676); John Templeton Foundation; H2020 European Research Council (ERC) (ERC-2016-STG-714151-PSINFONI); Australian Research Council (ARC)
