Studies with Liquid Helium Films

这个低温项目旨在了解氦膜的独特性质，并利用这些膜来解决凝聚态物理中感兴趣的问题。主要目的是研究He-3-He-4混合膜体系的新方面。这项工作将包括二维费米液体参数的确认，以及在极低温度下在4He薄膜上的二维3He中寻找新的超流体状态。实验还对氦薄膜在图案衬底上进行了一维和二维实验。感兴趣的话题包括二维定位和由于隐含的膜流可能引起的普适类的转移。实验技术包括石英晶体微平衡共振，He-4和He-3-He-4混合薄膜热性能的热容研究，以及图案衬底上氦薄膜的三声研究。除了有助于理解氦膜本身的行为外，这项工作还与费米系统、局部化和二维相变等现象有关。它还为研究生和本科生提供了良好的培训。学生获得尖端技术和基本概念的经验，为他们在学术界，政府或行业的职业生涯做好准备。本研究探讨了液氦的显著特性。这种研究提供了对自然界的独特见解，这是研究任何其他物质所无法获得的。研究表面上经过精心设计的氦薄膜的波动特性，可以更好地理解波是如何在新环境中被捕获的，以及施加的气流是如何改变这种行为的。研究两种自然存在形式的氦的薄膜混合物的动机是理论建议，一种新的超流体薄膜可能会被发现。这些混合薄膜的研究也使我们能够深入了解二维系统的物理学。参与这项工作的学生将获得使用精密仪器的实际研究经验。这种培训为他们在学术界、政府或工业界的职业生涯做准备。

This low temperature project seeks to understand the unique properties of helium films and to use these films to address problems of interest in Condensed Matter Physics. A primary objective is to study new aspects of the He-3-He-4 mixture film system. This work would include confirmation of two-dimensional Fermi liquid parameters and a search for a new superfluid state in the two dimensional 3He atop a 4He film at very low temperatures. Experiments are also conducted with helium films on patterned substrates in one and two dimensions. Topics of interest include two-dimensional localization and a possible shift of universality class due to an implied film flow. Experimental techniques include quartz crystal microbalance resonance, heat capacity studies of the thermal properties of He-4 and He-3-He-4 mixture films, and third sound studies of helium films on patterned substrates. In addition to contributing to progress in understanding the behavior of helium films themselves, the work has relevance to phenomena such as Fermi systems, localization, and two-dimensional phase transitions. It also provides excellent training for graduate students and undergraduates. The students gain experience in cutting edge technology and fundamental concepts that prepare them for careers in academe, government or industry.This research investigates the remarkable properties of liquid helium. Such study provides unique insights into nature that are not available by the study of any other substance. Study of the wave character of thin helium films on surfaces, that have been deliberately patterned, allows an enhanced understanding of how waves can be trapped in novel environments and of how an imposed flow can modify this behavior. The study of thin film mixtures of the two naturally occurring forms of helium is motivated by theoretical suggestions that a new kind of superfluid film may be found. These studies with mixture films also allow insight into the physics of two-dimensional systems. Students involved in this work gain hands-on research experience with sophisticated instrumentation. This training prepares them for careers in academe, government or industry.