Quantum Phase Transitions and Effects of Dissipation in Low-Dimensional Superconductors

这一个人研究人员奖将支持继续研究量子相变(QPT)的动力学，特别是耗散效应的项目。在过去的三年里，这个程序一直是新的实验数据和其他系统数据的重新分析的主要来源，这些数据表明在二维超导-绝缘-转变(SIT)薄膜中发生了相分离和“金属”相的存在。通过新的模型系统材料的选择，本项目将尝试完成存在耗散的二维SIT的真实相图。特别是，它将强调SIT系统在相变附近的电子微结构，相分离的问题，以及可能的耗散源。更深入地了解SIT与耗散问题，将有助于揭示高温超导、巨磁电阻和强关联磁体等突出问题。通过研究生的论文工作，本科生的参与，以及PI将设计的一门关于量子相干和耗散的新课程，该项目将继续具有强大的教育成分。许多物理系统，尽管本质上非常不同，可以用相似的物理原理来描述。因此，为突出的物理问题，特别是与基础科学和应用有关的问题找到合适的模型系统是至关重要的。二维薄膜中的超导体-绝缘体-相变(SIT)问题已经被证明是与理解高T_c超导体(对于超导电子学和用于功率处理的低损耗导体是重要的)以及二维电子气系统(对于量子极限中的电子器件应用是重要的)相关的物理。本方案扩展了我们对SIT系统的研究，纳入了更多的材料(即扩展了模型系统的参数空间)，并设计了新的探针来在微观尺度上研究该系统。该项目将继续通过研究生的论文工作、本科生的参与以及PI将设计的一门关于量子相干和耗散的新课程来继续发挥强大的教育作用。

This individual investigator award will support the continuation of a project to study the dynamics of Quantum Phase Transitions (QPT) and in particular the effects of dissipation. During the past three years this program has been a major source for new experimental data and re-analyses of data in other systems, that point to the occurrence of phase separation and the existence of "metallic" phases in two-dimensional Superconductor-Insulator-Transition (SIT) films. Through new choices of model-system materials the current project will try to complete the true phase diagram of two-dimensional SIT in the presence of dissipation. In particular it will emphasize the electronic microstructure of the SIT system near the transition, the issue of phase separation, and the possible sources of dissipation. Obtaining more insight into the SIT with dissipation problem will shed light on other outstanding problems such as high-Tc superconductivity, colossal magnetoresistance and strongly correlated magnets. Through graduate students thesis work, undergraduate students involvement, and a new course on quantum coherence and dissipation to be designed by the PI, the project will continue to have a strong educational component.%%%Many physical systems, although very different in nature, can be described by similar physical principles. Thus, finding appropriate model systems for outstanding physics problems, and in particular problems that relate to both, basic science and applications is of fundamental importance. The problem of Superconductor-Insulator-Transition (SIT) in two dimensional films has been shown to exhibit physics relevant to the understanding of high-Tc superconductors (important for superconductive electronics and low-loss conductors for power handling,) as well as to two-dimensional electron gas systems (important for electronic-device applications in the quantum limit.) The present program extends our study of SIT systems to include more materials (i.e. extending parameter space of the model system) and design new probes to study the system at the microscopic scale. The program will continue to have a strong educational component to it through graduate students thesis work, undergraduate students involvement, and a new course on quantum coherence and dissipation to be designed by the PI.***