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

该个人研究者奖将支持一个项目的继续研究量子相变（QPT）动力学，特别是耗散的影响。在过去的三年里，这个项目一直是新的实验数据的主要来源，并对其他系统的数据进行了重新分析，这些数据指出了二维超导体-绝缘体-过渡（SIT）薄膜中相分离和“金属”相的存在。通过对模型系统材料的新选择，本项目将尝试完成存在耗散的二维SIT的真实相图。特别地，它将强调在过渡附近的SIT系统的电子微观结构，相分离的问题，以及可能的耗散来源。对具有耗散问题的SIT的深入了解将有助于解决高tc超导性、巨磁阻和强相关磁体等其他突出问题。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，尽管性质大不相同，但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同时相关的问题，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-跃迁（SIT）问题已被证明展示了与理解高tc超导体（对超导电子学和低损耗导体的功率处理很重要）以及二维电子气体系统（对量子极限中的电子器件应用很重要）相关的物理学。本项目扩展了我们对SIT系统的研究，包括更多的材料（即扩展模型系统的参数空间），并设计新的探针在微观尺度上研究系统。该计划将继续通过研究生的论文工作，本科生的参与，以及由PI设计的关于量子相干性和耗散的新课程，具有很强的教育成分

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.***