Tests for BEC and/or Superfluid Behavior in Solid 4He

* 非技术摘要 ** 凝聚态物质在低温下显示出与我们的直觉相矛盾的性质。 其中最奇特的是超导性和超流性。 前者意味着某些金属在低于一定温度（其临界温度）时可以导电而不损失能量。 后者意味着低于临界温度的液氦具有零粘度，并且流动时没有能量损失。 例如，如果桶中的超流体与桶一起旋转，当桶停止时，超流体将继续旋转而不会减速，只要它保持在足够低的温度以保持超流体。另一个被预测的特殊性质是，即使是固体，固态氦也可以表现出超流性。 尽管有预测，但直到最近研究人员才可能观察到固体氦的这种性质。目前还不确定所观察到的行为是否是预期的“超固体”，但已经发现了一种新的，以前未知的物质状态。 该奖项将支持一个项目，其目标是确定这个新国家的性质。加州大学圣地亚哥分校的研究人员和约翰霍普金斯大学的同事们将使用各种实验技术来研究这种新的物质状态。 沿着对新物质状态的探索，本项目将提供一名研究生、一名博士后和一名本科生的培训。** 技术摘要 ** 固体氦是一种独特的材料，因为原子的结合非常弱，质量很小。 由于原子的波函数有异常大的重叠，这种材料可能会表现出不寻常的量子特性。 最戏剧性的可能性是，固体将同时表现出原子的结晶有序和玻色-爱因斯坦凝聚和/或超流体行为。 最近的实验结果发现了在非常低的温度下固体He中物质的新状态的证据。这种新的状态是否是理论上预测的“超固态”状态仍在研究中。该奖项将支持加州大学圣地亚哥分校的研究人员和约翰霍普金斯大学的同事们试图确定这种新状态的性质。各种实验，包括中子散射，热力学测量，声学/超声测量将被用来探索和识别这种状态的物质。 这项工作将使一名研究生、一名博士后和一名本科生发现一种新的物质状态，这将对我们对凝聚态的理解做出重要贡献。

*****NON-TECHNICAL ABSTRACT*******Condensed matter, at low temperatures, displays properties that contradict our intuition. The most peculiar of these are superconductivity and superfluidity. The former means that some metals can conduct electricity without loss of energy below a certain temperature (its critical temperature). The latter means that liquid helium below its critical temperature has zero viscosity and flows without loss of energy. For example, if a superfluid in a bucket is rotating with the bucket, when the bucket is stopped, the superfluid will continue to rotate without slowing down, as long as it is maintained at low enough temperature to remain a superfluid. Another peculiar property that has been predicted is that solid helium could also exhibit superfluidity even though it is a solid. Although predicted, it is only recently that researchers have possibly observed this property of solid helium. It is not yet certain whether the observed behavior is the anticipated "supersolid" however a new, previously unknown, state of matter has been discovered. This award will support a project with the objective identifying the nature of this new state. The researchers at the University of California, San Diego and colleagues at Johns Hopkins University will investigate this new state of matter using a wide variety of experimental techniques. Along exploring the new state of matter, this project will provide training for a graduate student, a post doc, and undergraduates. ****** TECHNICAL ABSTRACT*******Solid helium is a unique material in that the atoms are very weakly bound and have small mass. Due to unusually large overlap of the wave functions of the atoms, the material may exhibit unusual quantum properties. The most dramatic possibility is that the solid will exhibit at the same time both crystalline order of the atoms and a Bose-Einstein condensation and/or superfluid behavior. Recent experimental results have found evidence of a new state of matter in solid He at very low temperatures. Whether this new state is the theoretically predicted "supersolid" state is still under investigation. This award will support researchers at the University of California, San Diego and colleagues at Johns Hopkins University in their attempt to determine the nature of this new state. A variety of experiments including neutron scattering, thermodynamic measurements, and acoustic/ultrasonic measurements will be used to explore and identify this state of matter. The work will bring a graduate student, a post doc and undergraduates into the discovery of a new state of matter that will contribute importantly to our understanding of condensed matter.