title: Observation of the Zero Doppler Effect.
abstract: The normal Doppler effect has well-established applications in many areas of science and technology. Recently, a few experimental demonstrations of the inverse Doppler effect have begun to appear in negative-index metamaterials. Here we report an experimental observation of the zero Doppler effect, that is, no frequency shift irrespective of the relative motion between the wave signal source and the detector in a zero-index metamaterial. This unique phenomenon, accompanied by the normal and inverse Doppler effects, is generated by reflecting a wave from a moving discontinuity in a composite right/left-handed transmission line loaded with varactors when operating in the near zero-index passband, or the right/left-handed passband. This work has revealed a complete picture of the Doppler effect in metamaterials and may lead to potential applications in electromagnetic wave related metrology.
authors.affiliation: Tongji University, Shanghai, 200092, China.|Queen Mary University of London, E1 4NS, UK.
authors.forename: Jia
authors.initials: J
authors.lastname: Ran
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Yewen
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: University of Electronic Science and Technology of China, Chengdu, 610054, China.|Queen Mary University of London, E1 4NS, UK.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Chen
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Fang
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Junfei
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen