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A Newtonian approach to extraordinarily strong negative refraction


Metamaterials with negative refractive indices can manipulate electromagnetic waves in unusual ways, and can be used to achieve, for example, sub-diffraction-limit focusing1, the bending of light in the ‘wrong’ direction2, and reversed Doppler and Cerenkov effects2. These counterintuitive and technologically useful behaviours have spurred considerable efforts to synthesize a broad array of negative-index metamaterials with engineered electric, magnetic or optical properties1,2,3,4,5,6,7,8,9,10. Here we demonstrate another route to negative refraction by exploiting the inertia of electrons in semiconductor two-dimensional electron gases, collectively accelerated by electromagnetic waves according to Newton’s second law of motion, where this acceleration effect manifests as kinetic inductance11,12. Using kinetic inductance to attain negative refraction was theoretically proposed for three-dimensional metallic nanoparticles13 and seen experimentally with surface plasmons on the surface of a three-dimensional metal14. The two-dimensional electron gas that we use at cryogenic temperatures has a larger kinetic inductance than three-dimensional metals, leading to extraordinarily strong negative refraction at gigahertz frequencies, with an index as large as −700. This pronounced negative refractive index and the corresponding reduction in the effective wavelength opens a path to miniaturization in the science and technology of negative refraction.

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Figure 1: Device description.
Figure 2: Theory and simulation.
Figure 3: Temperature-dependent measurements.
Figure 4: Geometry-dependent measurements at 4.2 K.

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The authors are grateful for support for this research by the Air Force Office of Scientific Research under contract numbers FA 9550-09-1-0369 and FA 9550-08-1-0254. Device fabrication was performed in part at the Center for Nanoscale Systems at Harvard University. The authors thank W. F. Andress for assistance with device fabrication and microwave measurements.

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Authors and Affiliations



H.Y. and D.H. had the idea for the project. V.U. fabricated the 2DEG. H.Y. designed, fabricated and measured the properties of the devices. H.Y., K.Y.M.Y. and D.H. analysed the data. H.Y. and D.H. wrote the paper. All authors discussed the results and reviewed the manuscript.

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Correspondence to Donhee Ham.

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The authors declare no competing financial interests.

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Yoon, H., Yeung, K., Umansky, V. et al. A Newtonian approach to extraordinarily strong negative refraction. Nature 488, 65–69 (2012).

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