Mechanical Properties of Quantum Solids: Defects, Deformation and Flow

固体氦是“量子固体”的缩影--一种由量子力学控制其性质的晶体。在没有外部压力的情况下，量子运动可以防止氦冻结，即使在绝对零度下也是如此。在低温下，液氦表现出不同寻常的行为，包括一种壮观的现象--“超流”--这使得它可以完全不耗散地流动。氦可以通过加压结晶，但其性质仍然受量子效应的支配。一个令人震惊的预测是物质的一个新阶段，被称为“超固体”。2004年，扭转振荡器的质量解耦似乎终于出现了--这是超固体的预期特征。然而，经过十年的密集努力，人们已经清楚地看到，扭转振荡器的“去耦合”是一种人工制品，是固体氦弹性性质意外变化的结果，而不是超固体的迹象。这种被称为“巨塑性”的弹性行为反映了晶体缺陷的非凡流动性。在很低的温度下，位错可以自由滑动

Solid helium is the epitome of a “quantum solid” - a crystal whose properties are controlled by quantum mechanics. In the absence of external pressure, quantum motion prevents helium from freezing, even at absolute zero. At low temperatures, liquid helium exhibits unusual behavior, including a spectacular phenomenon – “superfluidity” – that allows it to flow with absolutely no dissipation. Helium can be crystallized by applying pressure but its properties are still dominated by quantum effects. One startling prediction is a new phase of matter known as a “supersolid”. In 2004, it appeared that mass decoupling from a torsional oscillator had finally been seen - the expected signature of supersolidity. However, after a decade of intensive effort it has become clear that the torsional oscillator “decoupling” was an artifact, the result of unexpected changes in solid helium’s elastic properties, not a sign of supersolidity. The elastic behavior, dubbed “giant plasticity”, reflects the extraordinary mobility of crystal defects. At very low temperatures dislocations glide freely through