Mettalic Behavior of Two-Dimensional Semiconductors

本项目将研究二维半导体中的金属-绝缘体（M-I）跃迁。这种现象是几年前在硅基二维电子系统中首次观察到的，后来又在其他二维系统中重现。尽管提出了几种模型（新型超导、非费米液态、维格纳玻璃的形成）和越来越多的理论和实验论文，但这种现象的潜在物理原理仍未被理解。在本项目中，将测量二维系统的电容和化学势，以及它们在毫开尔文温度下的输运和磁输运性质。这些测量将提供有关状态密度、可压缩性以及可能有关不寻常金属状态的磁性的信息。他们将展示这些性质如何在M-I跃迁和外部磁场中变化。所获得的信息对于理解二维M-I转换的性质至关重要。研究生和本科生将参与这项研究，从而在复杂而重要的前沿物理领域进行培训，熟悉半导体器件技术，并为未来在工业，政府或教育领域的就业做好充分准备。***该项目包括半导体材料特性的高级研究项目，其中电子之间的相互作用主导了物理特性，并经常导致新的，意想不到的现象。这项研究站在凝聚态物理和材料科学的前沿。本研究解决的问题具有根本性的重要性，其答案有望有助于在最基本的层面上理解材料。该项目将为研究生和本科生在物理学的前沿领域提供一个很好的介绍。他们将熟悉半导体技术，相关的研究方法，并将为未来在工业，政府或教育部门的就业做好准备。% % %

Metal-insulator (M-I)transitions in two-dimensional semiconductors will be investigated in this project. This phenomenon was first observed several years ago in silicon-base two-dimensional electron systems and later reproduced in other two-dimensional systems. The underlying physics of this phenomenon is not understood, in spite of several proposed models (new types of superconductivity, non-Fermi liquid state, formation of a Wigner glass) and a growing number of theoretical and experimental papers. In the present project, the capacitance and chemical potential of two-dimensional systems will be measured along with their transport and magneto-transport properties at milliKelvin temperatures. These measurements will provide information about density of states, compressibility, and possibly about magnetic properties of the unusual metallic state. They will show how these properties change at the M-I transition and in an external magnetic field. The information obtained is expected to be crucial for the understanding of the nature of the M-I transition in two dimensions. Graduate and undergraduate students will participate in this research and will thereby be trained in a complex and important area of forefront physics, become familiar with semiconductor device technology, and will be excellently prepared for future employment in industry, government or education. *** This project comprises an advanced research program in the properties of semiconductor materials, in which the interactions between electrons dominate the physical properties and often lead to new, unexpected phenomena. This research stands at the forefront of condensed matter physics and materials science. The questions addressed in this research are of fundamental importance, and the answers are expected to contribute to the understanding of materials at the most basic level. The project will provide an excellent introduction for graduate and undergraduate students in a cutting edge area of physics. They will become familiar with semiconductor technology, relevant research methods, and will be prepared for future employment in industry, government or education. %%%