Dynamics of the Wigner Electron Crystal on Liquid Helium Surfaces

在本研究计划中，我们研究了二维电子在液氦自由表面上的维格纳晶相动力学。为了阐明在垂直磁场作用下的电导率跃变、纵向电导率与驱动电压的比例以及液态^3He表面的非欧姆导电等非线性输运现象的机理，我们进行了实时观测非线性晶体动力学的实验，发展了一种新的实验方法，使用“t^2”电压脉冲，其前沿和后沿与时间的平方成比例地变化。该脉冲给出施加到晶体的驱动力的连续扫描。观察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转变。除了上述实验，我们还研究了^3He-^4He液体溶液自由表面上的电子。这为我们阐明液体的基本性质（^3He或^4He）对维格纳晶体动力学的影响提供了线索。我们测量了不同^3He浓度的液体混合物表面俘获的电子的电导率。然而，我们在磁场下观察到了异常共振现象。共振的特性类似于所谓的边缘磁等离子体激元的特性，其中等离子体振荡围绕电子片的周边传播。对这种意外共振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.