[论文解读] Strong Coupling Between RF Photons and Plasmons of Electrons on Liquid Helium

Asher Jennings, Ivan Grytsenko+7 more|arXiv (Cornell University)|Jan 30, 2026

Quantum, superfluid, helium dynamics被引用 0

一句话总结

本论文展示了液氦上漂浮电子等离子体与在LC谐振腔中被限制的射频光子之间的强耦合，并提供了时域的相干能量交换证据以及可调耦合。

ABSTRACT

Plasmons, arising from the collective motion of electrons, can interact strongly with electromagnetic fields or photons; this capability has been exploited across a broad range of applications, from chemical reactivity to biosensing. Recently, there has been growing interest in plasmons for applications in quantum information processing. Electrons floating on liquid helium provide an exceptionally clean, disorder-free system and have emerged as a promising platform for this purpose. In this work, we establish this system as a tunable plasmon-photon hybrid platform. We demonstrate strong coupling between floating-electron plasmons and radio-frequency (RF) photons confined in an LC resonator. Time-resolved measurements reveal coherent oscillatory energy exchange between the plasmonic and photonic modes, providing direct evidence of their coherent coupling. These results represent a step towards cavity quantum electrodynamics with a floating-electron plasmon coupled to a resonator. Furthermore, the LC resonator serves as a sensitive probe of electron-on-helium physics, enabling the observation of the Wigner crystal transition and a quantitative study of the temperature-dependent plasmon decay arising from ripplon-induced scattering.

研究动机与目标

• 研究在可调LC谐振腔中，液氦上电子等离子体模式与射频光子之间的强耦合。
• 表征电子密度、模态与温度如何影响耦合与耗散。
• 将LC谐振腔作为电子在氦上物理学的探针，包括Wigner晶体转变和 ripplon 散射。

提出的方法

• 用有效负载阻抗Z_p和耦合g在输入–输出框架内对等离子体–光子系统建模（Γ_ref方程）。
• 利用自洽电荷密度方法结合模拟的密度轮廓计算等离子体频率。
• 通过电子密度n_0和圆柱几何中的波向量k_{ν,μ}来调谐等离子体频率ω_p并提取Z_p。
• 通过实验测量反射谱以观察避让交叉并从拟合模型中提取g与γ_p。
• 进行时域微波反射测量以观测类似Rabi的能量交换并提取Λ_0。
• 研究γ_p的温度依赖性及通过Δ和g的变化探讨Wigner晶体转变。

Figure 1: (a) Experimental setup with Corbino-geometry electrodes forming part of an LC resonator. The device consists of radially arranged top and bottom electrodes, each with an area of approximately $0.5~\mathrm{cm}^{2}$ , which form the main capacitance $C$ of the LC resonator. The top center el

实验结果

研究问题

• RQ1 液氦上漂浮电子等离子体是否能与LC谐振腔中的射频光子实现强耦合？
• RQ2 电子密度、模态结构和温度如何影响耦合强度与等离子体衰减？
• RQ3 LC谐振腔是否可以作为探针用于Wigner晶体转变和ripplon介导散射的敏感检测？
• RQ4 该平台中等离子体与光子模之间能量交换的动力学行为（时域）是怎样的？

主要发现

• 实现强耦合，(g/2π)≈4.55–4.906 MHz，γ_p/2π≈3.30–5.10 MHz，伴随可观测的模态分裂Λ_0。
• 时域测量显示在零失谐附近等离子体与谐振腔模之间出现相干能量交换和类似Rabi振荡。
• 当ω_p≈ω_0时，LC谐振腔谱出现清晰的避免交叉，证实等离子体–光子混成。
• 等离子体衰减γ_p随温度升高而增加，与ripplon散射一致，并支持在约2–29 MHz范围内的Wigner晶体相关频移Δ，取决于条件。
• 在低温下，失谐Δ因Wigner晶体形成而发生偏移，指示与高库仑耦合模式一致的凹坑频率ω_d。
• 实验结果与等离子体频率及阻抗Z_p的自洽模拟高度一致，验证了建模方法。

Figure 2: Magnitude of the reflection coefficient $|\Gamma|$ as a function of $V_{\mathrm{BM}}$ and RF signal frequency $\omega/2\pi$ from both experiment in (a) and simulation in (c) for different $V_{\mathrm{BC}}=10,9,8,7.5,6,4$ V. $V_{\mathrm{BO}}$ is fixed to $-32$ V. (a) Measurement temperature