Compact self-matched gyrators using edge magnetoplasmons

TL;DR

This work introduces compact, self-impedance-matched gyrators based on edge magnetoplasmons in a GaAs/AlGaAs 2DEG, achieving controllable non-reciprocity with a sub-mm footprint and insertion losses of a few dB. By grounding one port and capacitive-coupling the others, the authors realize a three-peak, tunable frequency response whose gyration points align with transmission peaks, enabling on-chip integration without external matching networks. The experimental results, backed by a dissipative EMP model, yield quantitative access to EMP velocities, gate capacitance, and dissipation, and they demonstrate robust gyration up to $f \sim 1$ GHz with magnetic-field tunability. This approach offers a promising path toward scalable, low-loss non-reciprocal components for quantum information processing and interconnects, with potential extensions to magnetic-field-free platforms and gate-tunable variants.

Abstract

Non-reciprocal microwave components are indispensable in quantum information processing and cryogenic measurement. Conventional implementations, however, are bulky and incompatible with on-chip scalable integration. Recent efforts to develop compact on-chip alternatives often rely on active modulation or complex circuit architectures, which introduce additional losses and degrade performance. We demonstrate the realization of compact, self-impedance-matched gyrators based on edge magnetoplasmons in a two-dimensional electron gas. Gyrators can be used as building blocks for other non-reciprocal elements such as isolators and circulators. Our devices achieve gyration from 0.2 to 2 GHz, tunable by moderate out-of plane magnetic fields below 400 mT, and sub-mm footprint, two orders of magnitude smaller than conventional ferrite-based components. Using an electrode geometry predicted to minimize reflections, we achieve insertion losses as low as 2 to 4 dB. The self-matched design framework we utilize is broadly applicable, and can be implemented in a wide variety of non-reciprocal device architectures.

Figures (17)

• Figure 1: Device and measurement scheme. (a) Circuit model of the device. A magnetic field $B_\perp$ is applied out-of-plane causing chiral propagation of the EMP (blue and black arrows) along the edge (yellow). Port P3 is connected to ground. The pink dashed curves represent ungated sections. (b) Optical micrograph and microwave measurement setup of the large device. The circular mesa hosting a high-mobility 2DEG is false-colored in purple, with diameter $D$ (green arrow) and the contact overlap length $L$ (blue arrow). Measurements are done at $\sim$50. (c) Cross-sectional schematic along the dashed orange line in (b), showing the heterostructure (green and dark green) with the 2DEG (purple) located 90 nm below the surface and an aluminum gate overlapping the mesa.
• Figure 2: Phase response of the large device. (a) Phase of the forward transmission parameter $S_{21}$ after subtraction of the electrical delay. (b) Phase difference $\Delta\varphi$ between forward and reverse transmission. The red curves indicate points of gyration. Horizontal and vertical cuts at fixed frequency and magnetic field are shown in the bottom and side panels as indicated by the dashed lines.
• Figure 3: Magnitude response of the large device. (a) and (b) Magnitude of reverse ($|\overline{S}_{12}|$) and forward ($|\overline{S}_{21}|$) transmitted signal. The green and magenta dashed curves represent the lowest-frequency gyration mode. The black arrows serve to number the three peaks, as labeled. (c) Field cuts at 200, indicated by the orange and purple dashed lines in panels (a) and (b), sharing the same frequency axis. The black arrows and black dashed lines indicate the position of the magnitude peaks. (d) Insertion loss of peak 1, as indicated by the green and magenta dashed curves in panels (a) and (b).
• Figure 4: Non-reciprocity of two devices with different diameters. Non-reciprocity parameter $\Delta$ as a function of $B_\perp$ and frequency for two gyrators with diameters $D$ as labeled. The gyration modes appear as dark peaks, reaching maximum performance of $\Delta = 0.70$ at $B_\perp = \pm 70\,\text{mT}$ and $f = 400\,\text{MHz}$ for the large device, and $\Delta = 0.72$ at $B_\perp = \pm 62\,\text{mT}$ and $f = 940\,\text{MHz}$ for the small device.
• Figure 5: Model fitted to the large device. (a,b) Magnitude of $\overline{S}_{21}$ and $\overline{S}_{12}$ for the large device: experimental data at 200 (purple and red) compared with the fitted model (cyan and orange bands). The black line shows the dissipationless limit ($\delta = 0$). (c) Phase difference $\Delta\varphi$ of the large device: experimental data (green) compared with the model without additional delay (gray band) and with the linear shift introduced by an ungated delay $\tau_{\mathrm{ug}} \approx \qty{0.3}{\nano\second}$ (brown band).