Pattern of microscopic currents within a plasmonic wave. Figure credit: Justin Song.
Electrons in a metal can oscillate collectively to produce a wave called a “plasmon”. The properties of plasmons have found applications in many areas of science and technology, ranging from bioimaging to photodetection. Most notably, they can be used to compress and manipulate light at nanometer length scales, far below the wavelength of light waves in free space. However, the plasmons themselves have long been regarded as relatively simple, wave-like objects, lacking any interesting internal features.
Theoretical work by the group of Prof. Justin Song has challenged this assumption. In a paper published in April 2018 in Physical Review X, the team reports that plasmons in ordinary metals contain hidden internal structures that can affect their motion.
Asst. Prof. Justin Song and Dr. Li-kun Shi.
Much as a duck’s frantic paddling is hidden beneath the water surface as it glides across a pond, a plasmon that appears as a simple wave actually consists of swirling microscopic currents forming various intricate patterns. The researchers showed that these patterns can be exploited to alter the trajectory of the plasmons; for instance, plasmons reflecting from a surface undergo parallel shifts that can be controlled by a magnetic field.
In the future, this fundamental theoretical finding may lead to novel techniques for controlling plasmons in optical devices.
This work has been featured in the scientific news website Physics.
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