Studies of the Supersolid State of Matter

*非技术性摘要*物理学中的一个重要主题是研究宏观量子现象，或理解量子力学对宏观维度的原子或分子集合的影响。一种熟悉的宏观量子现象是超导，在这种现象中，电流可以在某些金属和氧化物中流动，在称为转变温度的特定温度以下完全没有电阻。一个相关的现象是超流现象，当液氦冷却到2K以下或绝对零度以上2度时，它在运动时可以永远流动。在前一个供资周期中，有一项了不起的发现；在0.2K以下的固体氦中也会出现这种超流现象。虽然这些实验已经被其他小组复制，但这种超固体行为还没有被理解。许多理论论文表明，超固态现象是氦晶体缺陷的结果。这个单独的研究项目将支持一项努力，以生长和表征最高质量的氦晶体，并寻找它们的超固体行为。如果成功，这一项目将有助于更好地了解这一现象。参与这项研究的研究生将接受实验物理方面的严格培训，并为在学术界和工业领域的职业生涯做好准备。他们还将参加由P.I.*技术摘要*带头开展的一系列K-12外联活动。这一个人研究人员奖支持对固体氦中超流性质的实验研究，这是在前一个资助期的一系列扭转振荡器实验中发现的。这一行为已经被其他实验室复制，然而关于超固体现象的许多问题仍然存在。到目前为止，所研究的固体样品的晶体质量还没有得到很好的表征，一些理论论文表明，所观察到的超固态行为是晶体中缺陷、位错和晶界的结果。我们将使用超声共振、X射线和热力学(热容)技术来生长和研究高质量的氦晶体，以加深我们对超固态行为的理解。参与这项研究的研究生将接受低温和精密测量技术方面的严格培训，从而为未来在学术界和工业领域的职业生涯做好准备。他们还将参加由P.I.带头的一系列K-12外展活动。

****NON-TECHNICAL ABSTRACT****An important theme in physics is the study macroscopic quantum phenomena, or understanding the effect quantum mechanics on a collection of atoms or molecules of macroscopic dimensions. A familiar macroscopic quantum phenomenon is superconductivity where electricity can flow in some metals and oxides with absolutely no resistance below some specific temperature called the transition temperature. A related phenomenon is superfluidity where liquid helium, when cooled below 2K or 2 degrees above absolute zero, can flow forever when it is set in motion. During the previous funding cycle a remarkable discovery was made; such a superflow also occurs in solid helium below 0.2K. While the experiments have been replicated by other groups, this supersolid behavior is not yet understood. A number of theoretical papers suggest the supersolid phenomenon is a consequence of imperfections in the helium crystal. This individual investigator project will support an effort to grow and characterize the highest quality helium crystals and to look for supersolid behavior in them. If successful this project will lead to a better understanding of the phenomenon. Graduate students involved in this research will receive rigorous training in experimental physics and will be well prepared for careers in academia and industries. They will also participate in a range of K-12 outreach activities spearheaded by the P.I..**** TECHNICAL ABSTRACT****This individual investigator award supports experimental investigations on the nature of superfluidity in solid helium, which was discovered in a series of torsional oscillator experiments during the prior funding period. This behavior has been replicated by other laboratories, however many questions concerning the phenomenon of supersolidity remain. The crystal quality of the solid samples studied to date has not been well characterized and a number of theoretical papers suggest the observed supersolid behavior is a consequence of defects, dislocations and grain boundaries in the crystals. High quality helium crystals will be grown and investigated using ultrasound resonance, x-ray, and thermodynamic (heat capacity) techniques in an effort to further our understanding of the supersolid behavior. Graduate students involved in this research will receive rigorous training in cryogenics and precision measurements techniques and thus will be well prepared for future careers in academia and industries. They will also participate in a range of K-12 outreach activities spearheaded by the P.I..