Studies of the Supersolid State of Matter

****非技术摘要****物理学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。一个熟悉的宏观量子现象是超导性，在某些特定的温度下，电流可以在某些金属和氧化物中完全没有电阻地流动，这种温度被称为转变温度。一个相关的现象是超流动性，当液氦冷却到2K以下或绝对零度以上2度时，当它启动时，它可以永远流动。在上一个筹资周期中，有了一个显著的发现；这种超流也发生在低于0.2K的固体氦中。虽然其他研究小组已经重复了这些实验，但这种超固体行为尚未被理解。许多理论论文认为，超固体现象是氦晶体缺陷的结果。这个个人研究项目将支持一项努力，以培养和表征最高质量的氦晶体，并在其中寻找超固体行为。如果成功，这个项目将有助于更好地理解这一现象。参与这项研究的研究生将接受严格的实验物理训练，并为在学术界和工业界的职业生涯做好准备。他们还将参加一系列由pi牵头的K-12外展活动。****技术摘要****该个人研究者奖支持对固体氦超流动性性质的实验研究，该研究是在先前资助期间的一系列扭转振荡器实验中发现的。这种行为已经被其他实验室复制，但是关于超固体现象仍然存在许多问题。迄今为止所研究的固体样品的晶体质量尚未得到很好的表征，许多理论论文认为观察到的超固体行为是晶体中缺陷、位错和晶界的结果。高质量的氦晶体将通过超声共振、x射线和热力学（热容）技术来生长和研究，以进一步了解超固体行为。参与这项研究的研究生将接受低温学和精密测量技术的严格培训，从而为未来在学术界和工业界的职业生涯做好充分的准备。他们还将参加一系列由pi牵头的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..