Novel SuperLattice Plasmon Mode in a Grating of 2D Electron Strips

Abstract

We investigate GaAs/AlGaAs heterostructure membranes with a metasurface made up of a grating of two-dimensional electron system (2DES) strips. Experiments have revealed a strong plasma resonance in the transmission of the metasurface. We have found that a collective effect from the superlattice, along with lateral screening between the strips, leads to the emergence of a new plasmon mode in the metasurface under study. Furthermore, we develop an analytical approach that accurately describes the behavior of the discovered superlattice plasmon mode, providing new insights into the fundamental physics of plasmonic metasurface systems.

Figures (4)

• Figure 1: (Left) E-beam photo of the sample comprising a grating of isolated 2DES strips. The area of the 2DES is highlighted in yellow. Each 2DES strip has a width of $w = 23$ µm, and the period is $p = 25$ µm. (Right) Schematic of the plasmonic metasurface device. The two-dimensional electron system is represented in yellow, while the GaAs substrate is shown in blue. The coordinate system is provided in both panels to indicate the orientation of the structures and to facilitate comparison between the micrograph and the schematic.
• Figure 2: The normalized transmission spectra of three samples with different strip spacings, specifically $h = 12$, $3.5$, and $1.3$ µm. All three samples share the same period, $p = 25$ µm. For clarity, the curves have been vertically shifted by $1$ unit. The inset shows the transmission spectrum of the $h = 3.5$ µm sample without normalization. The solid red line represents the Fabry-Pérot function (\ref{['FP']}) for the bare dielectric membrane with no 2DES.
• Figure 3: Dependence of the plasmon frequency on the $h/p$. The period of the plasmonic metasurface was maintained at a fixed value of $p = 25$ µm. The solid red line represents a theoretical prediction (\ref{['NewPlasmon']}), while the blue line presents the standard 2D plasmon frequency (\ref{['Plasmon']}) in a single strip with wave vector $q=3 \pi/4w$. The solid black line shows the result of simulation in the HFSS 3D high-frequency simulation software. The dotted curve in Fig. \ref{['3']} depicts the result for the analytical prediction from Velizhanin:2015. Top inset displays the color maps of field-$|E|$ distribution at the plasmon resonance for $h=0.25$, $2.5$, and $12.5$ µm ($p = 25$ µm). The 2DES strip is located at the center of each color map.
• Figure 4: Magnetodispersion of the observed plasma resonance. The dashed line denotes the cyclotron resonance $\omega_c = e B/m^{\ast}$. The solid line represents the hybrid magnetoplasma law $\omega^2 = \omega_{sp}^2 + \omega_c^2$. The metasurface strip width is $w = 23.7$ µm, with a period of $p = 25$ µm.