Critical couplings in topological-insulator waveguide-resonator systems observed in elastic waves
National Laboratory of Solid State Microstructures & Department of Materials Science and Engineering, Nanjing University（南京大学固态微结构实验室与材料科学与工程系）；Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University（南京大学江苏省人工功能材料重点实验室）
Waveguides and resonators are core components in the large-scale integration of electronics, photonics, and phononics, both in existing and future scenarios. In certain situations, there is critical coupling of the two components; i.e., no energy passes through the waveguide after the incoming wave couples into the resonator. The transmission spectral characteristics resulting from this phenomenon are highly advantageous for signal filtering, switching, multiplexing, and sensing. In the present study, adopting an elastic-wave platform, we introduce topological insulator (TI), a remarkable achievement in condensed matter physics over the past decade, into a classical waveguide-ring-resonator configuration. Along with basic similarities with classical systems, a TI system has important differences and advantages, mostly owing to the spin-momentum locked transmission states at the TI boundaries. As an example, a two-port TI waveguide resonator can fundamentally eliminate upstream reflections while completely retaining useful transmission spectral characteristics, and maximize the energy in the resonator, with possible applications being novel signal processing, gyro/sensing, lasering, energy harvesting, and intense wave-matter interactions, using phonons, photons, or even electrons. The present work further enhances the confidence of using topological protection for practical device performance and functionalities, especially considering the crucial advantage of introducing (pseudo)spins to existing conventional configurations. More in-depth research on advancing phononics/photonics, especially on-chip, is foreseen.
Optimization of Coplanar Waveguide Resonators for ESR Studies on Metals
本文对高导电金属样品附近共面波导谐振器的电磁微波场进行了模拟和解析计算。CPW结构的设计目的是研究金属重费米子系统中的电子自旋共振（ESR），特别是YbRh $_2$ Si $_2$，接近量子临界点。利用CPW谐振器进行ESR实验，可以在mK温度和广泛的自由选择频率范围内进行研究。因此，它是非常感兴趣的，以评估附近的金属样品的共振共面波导结构的性能。在这里，我们研究的微波场在样品表面的波导结构的样品距离的函数和分析的影响的样品上的谐振器的性能。模拟结果揭示了一个最佳的样品距离的微波磁场在样品中最大化，因此最适合ESR研究。
