Theory of micro-wave absorption of 2-dimensional Wigner crystals

1.指出硅- mos等半导体异质结构界面上的二维电子受氧化物中杂质的影响发生局域-离域跃迁。我们已经用路径积分的形式表明，当电子形成电子晶体或维格纳晶格时，维格纳声子谱在长波长度极限处有一个能隙，并且电子是局域化的。由于维格纳声子的态密度，微波吸收的线形不是洛伦兹型的，而是不对称的。Kono等在极低温度下测量了液氦3上准二维电子的等离子激元共振，发现(a)共振位置几乎与温度无关，(b)线宽与温度大致成正比。假设二维电子形成与液氦表面毛细波或波纹相互作用的维格纳晶体，利用路径积分法得到的线性交流电导率公式计算了等离子体共振的线宽。结果表明，线宽与温度成正比，与实验结果吻合较好。这种温度依赖性来自散射体的数量，即热激发波纹的数量。

1.It is pointed out that 2-dimensional electrons located at the interface of semiconductor hetero-structures such as Si-MOS experience the localized-delocalized transition by the influence of impurities in oxides. We have shown by using the path-integral formalism that when electrons form an electron crystal or Wigner lattice, the Wigner phonon spectra have an energy gap in the long wave-length limit, and that the electrons are localized. The line-shape of the micro-wave absorption is not of the Lorentzian type but asymmetric owing to the density of states of the Wigner phonons.2.Kono et al. measured the plasmon resonance of quasi-2-dimensional electrons on liquid helium 3 at very low temperatures and found that (a) the resonance position is almost independent of temperature, and (b) the line-width is roughly proportional to temperature. By assuming that the 2-dimensional electrons form a Wigner crystal which interacts with the surface capillary waves or ripplons of liquid helium, we have calculated the line-width of the plasmon resonance by the linear ac conductivity formula obtained by the path-integral method. The results show that the line-width is proportional to temperature and is in good agreement with experiments. This temperature dependence comes from the number of scatterers, i. e., of thermally excited ripplons.