Supersolidity and the Supersolid to Normal Solid Transition

超固体和超固体到普通固体的转变

• 批准号: 1103159
• 负责人: Moses Chan
• 金额: $ 92.5万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1103159&HistoricalAwards=false
• 关键词: Supersolidity; Supersolid; Normal; Solid; Transition

Technical Abstract.The observation of superfluid-like behavior in bulk solid helium and solid helium confined in porous media in the P.I.'s laboratory has been replicated in a dozen other laboratories. Quantum Monte Carlo simulations suggest superfluidity is not possible in a perfect crystal but dislocation lines may be superfluid. Shear modulus measurements indicate that superfluidity in solid helium or supersolidity is the consequence of a stiffened network of interconnected dislocation lines. This model however, cannot explain the results in porous media since it is difficult to envision dislocation lines inside a pore of a few nm. Three questions will be addressed in this project. One set of experiments will determine if supersolidity is possible in a perfect crystal with little or no dislocation lines. Secondly, heat capacity, thermal conductivity measurements will be carried out to determine how supersolidity in porous media is different from that in bulk solid. Lastly torsional oscillator measurements will be made to determine the spatial extent of quantum phase coherence in a supersolid system. The experiments are exceptionally challenging hence providing an excellent training ground for the post-doctoral, graduate and undergraduate students in the project. The P.I. has a very strong and sustained record in training students for successful scientific careers in academia and in industrial and government laboratoriesNon-technical AbstractWhen liquid helium is cooled below -271 Celsius, or 2 K above absolute zero, it enters the superfluid state with zero viscosity allowing it to flow relative to the walls of a container with no friction. What this means is that if a container is being oscillated back and forth, the superfluid inside will sit perfectly still. Like superconductivity, superfluidity is a manifestation of quantum mechanics at macroscopic scales. In 2004, the P.I. and one of his former student found evidence that below 0.2K, a small fraction (on the order of 1%) of a solid helium sample would remain stationary when its container is being oscillated. This experiment, since replicated in a dozen laboratories worldwide, indicates the existence of superfluidity in a solid, more conveniently called supersolidity. The discovery of this new state of matter has created considerable excitement in the physics community and beyond. An outstanding question of the phenomenon is whether supersolidity is possible in a perfect helium crystal or it requires the presence of defects such as dislocation lines in the crystal. The experiments proposed in the project are designed to resolve this question and will be carried out by post-doctoral, graduate and undergraduate students. The P.I. has a very strong and sustained record in training students for successful scientific careers in academia, industrial and government laboratories.

技术摘要：在P.I.实验室中观察到了大块固体氦和受限于多孔介质中的固体氦的类超流行为。他的实验室已被其他十几个实验室复制。 量子蒙地卡罗模拟表明，在完美的晶体中，超流性是不可能的，但位错线可能是超流性的。剪切模量的测量表明，在固体氦或超固体的超流性是一个相互连接的位错线硬化网络的结果。然而，该模型不能解释多孔介质中的结果，因为很难想象几nm的孔内的位错线。本项目将解决三个问题。其中一组实验将确定在几乎没有位错线的完美晶体中是否有可能实现超固态。其次，通过比热容、导热系数的测量来确定多孔介质中的超固体性与块体固体中的超固体性有何不同。最后，将通过扭转振子测量来确定超固体系统中量子相位相干的空间范围。这些实验极具挑战性，因此为该项目的博士后，研究生和本科生提供了一个很好的培训基地。私家侦探在培养学生在学术界、工业界和政府实验室的成功科学事业方面有着非常强大和持续的记录。非技术摘要当液氦冷却到-271摄氏度以下，或绝对零度以上2 K时，它进入零粘度的超流体状态，使其能够相对于容器壁无摩擦地流动。这意味着，如果一个容器被来回振荡，里面的超流体将完全静止。 与超导性一样，超流性是量子力学在宏观尺度上的表现。2004年，P.I.他以前的一个学生发现，在0.2K以下，当容器振荡时，固体氦样品的一小部分（约1%）将保持静止。这个实验在全世界十几个实验室重复进行，表明固体中存在超流性，更方便地称为超固体。这种新物质状态的发现在物理学界和其他领域引起了相当大的兴奋。这一现象的一个突出问题是，在一个完美的氦晶体中是否可能存在超固态，或者它需要晶体中存在位错线等缺陷。该项目中提出的实验旨在解决这个问题，并将由博士后，研究生和本科生进行。私家侦探在培养学生在学术界，工业和政府实验室成功的科学事业方面有着非常强大和持续的记录。