Quantum Many - Body Effect of Two - Dimensional Electron Systems on Helium Films

氦薄膜上二维电子系统的量子多体效应

基本信息

批准号：
14340110
负责人：
SHIRAHAMA Keiya
金额：
$ 8.58万
依托单位：
Keio University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

We have investigated a two - dimensional (2-D) electron system formed on a superfluid helium film. A variety of novel quantum phenomena such as quantum melting of the Wigner crystal, a low - density quantum fluid state and its quantum Hall effects have been expected for the electrons on high - dielectric constant materials. However, experiments have failed to realize stable 2-D electrons. In this study we have attempted to form 2-D electrons and to make conductivity measurement. The results are summarized as follows:1. We have made and constructed a dilution refrigerator, a ^4He cryostat, and a AC conductivity measurement setup. We have developed a novel conductivity cell, in which the height of helium surface is controlled by a piezoelectric motor. This makes a fine thickness. We have employed an atomically flat sapphire substrate (dielectric constant 〜9). We have succeeded to form the very low density electrons, and taken conductivity data in a wide range of temperature.2. In order to control the coupling of the electrons to helium surface excitations (ripplons), we have conducted the conductivity measurement for electrons on ^3He - ^4He liquid mixtures. We have quite unexpectedly observed resonance phenomena under perpendicular magnetic field. We have revealed that the resonances result from an inhomogeneity of electron density, and the addition of ^3He atoms to liquid ^4He enhances and stabilizes the density inhomogeneity.We have observed an anomalous nonlinear transport phenomenon in the 2-D Wigner crystal on liquid ^3He revealed theoretically that the nonlinearity is attributed to a strong damping effect inherent in liquid ^3He. This finding gives an important clue for future experiments on electrons on ^3He films at ultraslow temperatures.

我们研究了在超流氦薄膜上形成的二维（2-D）电子系统，研究了维格纳晶体的量子熔化、低密度量子流体态及其量子霍尔效应等多种新颖的量子现象。然而，实验未能实现稳定的二维电子。在本研究中，我们尝试形成二维电子并进行电导率测量，结果总结如下：1。。我们制作并构建了稀释制冷机、^4He 低温恒温器和交流电导率测量装置，我们开发了一种新型电导率单元，其中氦表面的高度由压电电机控制，这使得我们可以实现精细的厚度。采用原子级平坦的蓝宝石衬底（介电常数~9），我们成功地形成了非常低密度的电子，并在很宽的温度范围内获取了电导率数据。2．电子到氦表面激发（波纹），我们对 ^3He - ^4He 液体混合物进行了电导率测量，我们在垂直磁场下观察到了共振现象，我们发现共振是由电子的不均匀性引起的。密度，并且向液体^4He添加^3He原子增强并稳定了密度不均匀性。我们观察到了异常的非线性输运现象液体 ^3He 上的二维维格纳晶体从理论上揭示了非线性归因于液体 ^3He 固有的强阻尼效应，这一发现为未来超低温度下 ^3He 薄膜上的电子实验提供了重要线索。