SGER: An Experiment to Understand the Apparent "Supersolid" Behavior of Solid 4He

********非技术摘要*****最近宣布了一个惊人的发现：在极低的温度和高压下，氦原子明显地在没有摩擦的情况下流过固体氦。这一声明令人吃惊，因为普通固体的行为是这样的，虽然固体中的原子会有一点摆动，但它们通常是原地不动的。通常的经验是，当你捡起一块石头时，固体不会漏出来。这项探索性研究小额赠款（SGER）将支持一个项目，该项目将在各种温度和压力下，探索在固体氦块两侧的两个液氦储层之间施加的压力差是否会因原子流过固体氦而松弛。固体两侧的储层将是液态的，这种液态是由高度多孔材料中氦的独特性质维持的。如果原子确实在固体中流动，这项研究将有助于确定这一过程发生的真正机制。而且，如果存在这样的流动，其他实验将试图使流动通过一个甜甜圈形状的固体氦样品发生，并确定这种流动是否持续-即能够在一个闭环中流动而不减速。也就是说，该研究将探索是否有可能在固体中存在无摩擦的超流。实验时间紧迫，因为这个区域非常活跃；世界各地的研究小组都在努力寻找不同的方法来证实这种奇怪状态的存在。虽然发现的时机已经成熟，但这样的工作也有风险，迄今为止的一些实验得出了意想不到的负面结果。确认这种奇怪固体的存在将对我们对“物质量子态”的理解产生重大影响。研究生将参与实验，因此他们将接受培训，以获得博士学位，并最终进入科学工作队伍。********技术摘要*****这个SGER支持的研究，旨在为Kim和Chan在固体氦中观察到的惊人观察背后的真实物理学提供实质性的见解，他们观察到扭转振荡器的惯性矩变化，并将观察解释为物质新状态的证据，即“超固体”。第一个实验将把固体氦放在多孔材料Vycor中所含的氦附近，这样就有可能创造一个条件，在高于正常熔化曲线的压力下，液氦可以与固体氦接触。实验将试图确定在固体氦圆柱体两侧的两个储层之间施加的压力差是否可以通过氦原子通过固体的流动而松弛，以及这种流动如何随固体的基本压力而变化。当实验完成后，这些实验将对“超固体”的真实性质提供相当深入的了解，并有助于阐明这种流动发生的具体机制。如果这种流动以合理的临界速度被检测到，接下来的实验将寻求建立一个环形几何形状的持续流动，并证明这种流动确实是持续的。实验时间紧迫，因为这个区域非常活跃；世界各地的研究小组都在努力寻找不同的方法来证实“超固体”状态的存在。虽然发现的时机已经成熟，但这样的工作也有风险，迄今为止的一些实验得出了意想不到的负面结果。确认“超固体”状态的存在将对我们对物质量子态的理解产生重大影响。研究生将参与实验，因此他们将接受培训，以获得博士学位，并最终进入科学工作队伍。

********NON-TECHNICAL ABSTRACT*****Recently a startling discovery was announced: At very low temperatures and elevated pressures atoms of helium apparently flow though solid helium without friction. This announcement was startling because ordinary solids behave themselves and while atoms in a solid wiggle a bit, they generally stay put. It is common experience that when you pick up a rock, none of the solid leaks out. This Small Grant for Exploratory Research (SGER) will support a project that will, under a variety of temperatures and pressures, explore whether a pressure difference applied between two liquid helium reservoirs on either side of a block of solid helium will relax by the flow of atoms through the solid helium. The reservoirs on either side of the solid will be liquid, maintained in that state by the unique properties of helium in a highly porous material. If atoms do indeed flow through the solid, this research will help to determine the true mechanism by which this takes place. And, if such flow is present, other experiments will attempt to cause the flow to take place through a donut-shaped sample of solid helium and determine whether such flow is persistent - i.e. able to flow in a closed loop without slowing down. That is, the research will explore whether it is possible for there to be friction-free super-flow in a solid. The experiments are time-urgent since this area is extremely active; with groups around the world intensely pursuing different approaches in attempts to confirm the existence of this strange state. While ripe for discovery, such work is also risky, with some experiments to date yielding unexpected negative results. Confirming the existence of this strange solid would have a large impact our understanding of "quantum states of matter." Graduate students will be involved in the experiments and thus they will receive training that will lead to a Ph.D. and their eventual entry into the scientific workforce.******** TECHNICAL ABSTRACT*****This SGER supports research seeking to provide substantial insight into the true physics behind the startling observations of Kim and Chan seen in solid helium in which they observed a moment of inertia change in a torsional oscillator and interpreted the observation as evidence for a new state of matter, a "supersolid". The first experiments will place solid helium adjacent to helium contained in the porous material Vycor, by which it is possible to create a condition in which liquid helium can interface solid helium at pressures above the normal melting curve. The experiments will seek to establish whether a pressure difference imposed between the two fluid reservoirs on two sides of a cylinder of solid helium can relax by the flow of helium atoms through the solid and how such flow may vary with the base pressure of the solid. When completed, these experiments should shed considerable insight into the true nature of the "supersolid" and help to elucidate the specific mechanism by which such flow takes place. If such flow is detected with reasonable critical velocity, the next experiments will seek to establish a persistent flow in a torus-shaped geometry and document that the flow is indeed persistent. The experiments are time-urgent since this area is extremely active; with groups around the world intensely pursuing different approaches in attempts to confirm the existence of the "supersolid" state. While ripe for discovery, such work is also risky, with some experiments to date yielding unexpected negative results. Confirming the existence of a "supersolid" state would have a large impact on our understanding of quantum states of matter. Graduate students will be involved in the experiments and thus they will receive training that will lead to a Ph.D. and their eventual entry into the scientific workforce.