Abstract
Anisotropic plasmonic surface supports elliptic, hyperbolic and even flattened polaritons, which is quite interesting for the diffractionless and highly collimated propagation of infrared light at the nanoscale. However, direct real-space near-field observation of anisotropic plasmons as well as frequency dependent topological transitions in natural materials have not been realized. In this paper, we theoretically investigate real-space anisotropic plasmons in WTe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin films by using a phenomenological cavity model, anisotropic near-field plasmonic images with specific interference patterns and isofrequency curves in momentum space have been demonstrated. Due to the frequency selective forbidden of plasmons along <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</i> axis, a topological transition from the elliptic to the hyperbolic regime is manifested. Moreover, the plasmons as well as topological transition present significant electrostatic-gating tunability. Our studies provide new insights into WTe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> based plasmonic components for the manipulation of plasmon propagation, which capable of tailoring anisotropic two-dimensional light confinement in the far-infrared regime and can be applied to investigate other anisotropic materials.
Highlights
S URFACE plasmon polaritons (SPPs) are coupled excitations of mobile electrons and electromagnetic fields that enable confinement and control light in nanoscale devices [1,2,3,4,5]
Our results reveal a tunable and scalable anisotropic plasmonic platform for applications in sensing, imaging, and light modulation
The plasmon dispersion along a and b axes are plotted as a pseudocolor map in Fig. 4, it is obvious that the hyperbolic regime is located in the range of 425-630 cm-1, where the imaginary part of conductivity is positive along a axis
Summary
S URFACE plasmon polaritons (SPPs) are coupled excitations of mobile electrons and electromagnetic fields that enable confinement and control light in nanoscale devices [1,2,3,4,5]. Noble metals such as gold and silver are common platforms supporting plasmons in visible and near-infrared frequency range [6,7,8], the higher carrier concentration and lower carrier mobilities result in larger absorption losses [9]. Our results reveal a tunable and scalable anisotropic plasmonic platform for applications in sensing, imaging, and light modulation
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