Dynamics of the Wigner Electron Crystal on Liquid Helium Surfaces

在这个研究项目中，我们研究了捕获在液氦自由表面上的二维电子的维格纳晶相的动力学。为了阐明非线性输运现象的机制，包括(1)垂直磁场下的电导率跳跃，(2)纵向电导率与驱动电压的比例，以及(3)液体^3He表面的非欧姆电导，我们进行了实时观察非线性晶体动力学的实验。我们发展了一种新的实验方法，采用“t^2”电压脉冲，其前沿和后缘与时间的平方成比例变化。该脉冲对施加到晶体的驱动力进行连续扫描。观测到的响应清楚地显示了滑动行为，揭示了晶体的外力决定了滑动跃迁。此外，我们还研究了^3He-^4He液体溶液自由表面上的电子。它给我们提供了一条线索，以阐明潜在的液体性质(^3He或^4He)对Wigner晶体动力学的影响。我们对不同~3He浓度的液体混合物表面捕获的电子进行了电导测量。然而，我们观察到了磁场下的反常共振现象。这种共振的特性类似于所谓的边缘磁等离子体的特性，在边缘磁等离子体中，等离子体振荡围绕电子薄片的周长传播。对这种意想不到的共鸣的进一步研究正在进行中。

In this research project, we studied the dynamics of the Wigner crystal phase of two-dimensional electrons trapped on free surfaces of liquid helium. In order to elucidate the mechanisms of nonlinear transport phenomena including (1) the conductivity jump, and (2) proportionality of the longitudinal conductivity to the driving voltage, under a perpendicular magnetic field, and (3) the non-Ohmic conduction on a liquid ^3He surface, we have conducted experiments to make a real-time observation of the nonlinear crystal dynamicsWe have developed a new experimental method, using a "t^2" voltage pulse, whose leading and trailing edges change in proportion to the square of time. This pulse gives a continuous sweep of the driving force applied to the crystal. The observed response clearly shows the sliding behavior, revealing that the external force to the crystal determines the sliding transition.In addition to the above experiments, we have studied the electrons on the free surface of ^3He-^4He liquid solutions. It offers us a clue to elucidate the effect of the underlying liquid properties(^3He or ^4He) to the dynamics of the Wigner crystal. We have made a conductivity measurement of the electrons trapped on the liquid mixture surfaces with various ^3He concentrations. However, we have observed anomalous resonance phenomena under a magnetic field. The characteristics of the resonance are similar to the properties of so-called edge magnetoplasmons, in which the plasma oscillation propagates around the perimeter of the electron sheet. Further studies of this unexpected resonance are underway.