Frequencies of the Edge-Magnetoplasmon Excitations in Gated Quantum Hall Edges

Abstract: We have investigated microwave transmission through the edge of quantum Hall systems by employing a coplanar waveguide (CPW) fabricated on the surface of a GaAs/AlGaAs two-dimensional electron gas (2DEG) wafer. An edge is introduced to the slot region of the CPW by applying a negative bias $V_\mathrm{g}$ to the central electrode (CE) and depleting the 2DEG below the CE. We observe peaks attributable to the excitation of edge magnetoplasmons (EMP) at a fundamental frequency $f_0$ and at its harmonics $i f_0$ ($i$ = 2, 3,...). The frequency $f_0$ increases with decreasing $V_\mathrm{g}$, indicating that EMP propagates with higher velocity for more negative $V_\mathrm{g}$. The dependence of $f_0$ on $V_\mathrm{g}$ is interpreted in terms of the variation in the distance between the edge state and the CE, which alters the velocity by varying the capacitive coupling between them. The peaks are observed to continue, albeit with less clarity, up to the regions of $V_\mathrm{g}$ where 2DEG still remains below the CE.