Studies with Liquid Helium Films

这个低温项目旨在了解氦薄膜的独特性质，并利用这些薄膜来解决凝聚态物理中感兴趣的问题。一个主要的目标是研究He-3-He-4混合薄膜系统的新方面。这项工作将包括确认二维费米液体参数，以及在极低温度下在4He薄膜上的二维3He中寻找新的超流状态。我们还在一维和二维的图案化衬底上进行了氦膜实验。感兴趣的主题包括二维局部化和由于隐含的薄膜流动而可能引起的普适性类的移动。实验技术包括石英晶体微天平共振，He-4和He-3-He-4混合薄膜热容研究，以及图案化衬底上氦薄膜的第三声学研究。除了有助于理解氦薄膜本身的行为之外，这项工作还与费米系统、局域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。学生在尖端技术和基本概念方面获得经验，为他们在学术、政府或行业的职业生涯做准备。这项研究调查了液氦的显著性质。这种研究提供了对自然界的独特见解，这是任何其他物质的研究都无法获得的。研究表面上被刻意图案化的薄氦薄膜的波动特性，可以更好地理解波如何被困在新的环境中，以及施加的气流如何改变这种行为。对这两种自然存在的氦的薄膜混合物的研究是由理论上的建议推动的，即可能会发现一种新的超流体薄膜。这些关于混合膜的研究也让我们得以深入了解二维系统的物理。参与这项工作的学生可以通过使用复杂的仪器获得实践研究经验。这项培训为他们在学术界、政府或行业的职业生涯做好了准备。

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.