Sasaki Satoshi, Caupin Frédéric, Balibar Sébastien
Laboratoire de Physique Statistique de l'Ecole Normale Supérieure associé au CNRS et aux Universités Paris 6 et Paris 7, 24 rue Lhomond 75231 Paris Cedex 05, France.
Phys Rev Lett. 2007 Nov 16;99(20):205302. doi: 10.1103/PhysRevLett.99.205302. Epub 2007 Nov 15.
We have observed boundaries between hcp 4He crystal grains in equilibrium with liquid 4He. We have found that, when emerging at the liquid-solid interface, a grain boundary makes a groove whose dihedral angle 2theta is nonzero. This measurement shows that grain boundaries are not completely wet by the liquid phase, in agreement with recent Monte Carlo simulations. Depending on the value of theta, the contact line of a grain boundary with a solid wall may be wet by the liquid. In this case, the line is a thin channel with a curved triangular cross section, whose measured width agrees with predictions from a simple model. We discuss these measurements in the context of grain boundary premelting and for a future understanding of the possible supersolidity of solid 4He.
我们观察到了与液态(^4)He处于平衡状态的六方密堆积（hcp）(^4)He晶粒之间的边界。我们发现，当晶界出现在液固界面时，会形成一个沟槽，其二面角(2\theta)不为零。该测量结果表明，液相并未完全浸润晶界，这与最近的蒙特卡罗模拟结果一致。根据(\theta)的值，晶界与固体壁的接触线可能会被液体浸润。在这种情况下，该线是一个具有弯曲三角形横截面的细通道，其测量宽度与一个简单模型的预测结果相符。我们在晶界预熔的背景下讨论这些测量结果，并期望未来能对固态(^4)He可能的超流性有所理解。
