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O: Fachverband Oberflächenphysik
O 43: Plasmonics and Nanooptics III: Periodic Structures and Theory
O 43.7: Vortrag
Dienstag, 17. März 2020, 12:00–12:15, WIL A317
Optical Nano-Imaging of Electronic Shear Modes — Jun Yong Khoo1, Po-Yao Chang2,1, Inti Sodemann1, and •Falko Pientka1 — 1Max-Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany — 2Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
Plasmons are collective excitations of metals that consist of modulations of the electron density similar to compressional waves in classical liquids, which allows for an efficient coupling to light. In addition, moderately interacting two-dimensional metals can feature a second type of collective mode, involving electron motion transverse to the propagation direction. Such shear modes are akin to transverse sound waves in a crystal and have no counterpart in classical liquids. Experimental evidence of such shear modes has remained elusive so far, as a lack density fluctuations strongly suppresses the coupling to light. Here, we show that shear modes can nevertheless be probed by optical techniques in the presence of a static magnetic field. Specifically, we predict signatures in scanning near-field optical microscopy, where spatial oscillations of the near-field signal at the wavelength of the shear mode emerge as the field strength is increased. Our proposals is largely based on existing experimental technology operating at frequencies in the far infrared to terahertz regime.