二维和准二维固体~ 4 He的基态性质和超流性
Ground-state properties and superfluidity of two- and quasi two-dimensional solid 4He
摘要：
在最近的一项研究中，我们报道了一种新型的试探波函数，它在粒子交换下是对称的，并且能够描述超固相。在本工作中，我们使用扩散蒙特卡罗方法和这个模型的波函数来研究固体4 He在二维和准二维几何中的性质。在纯二维的情况下，我们得到的总基态能量和冻结和熔化的密度与以前的精确的Monte Carlo计算结果进行了一个略有不同的原子间势模型是很好的协议。我们计算了二维固体4 He的零温超流率ρ_{s} / ρ的值，发现在所有考虑的情况下，它都可以忽略不计，这与用同样的计算方法在完美（无缺陷）三维晶体中得到的结果相似。有趣的是，通过允许原子在垂直于它们被限制在零点振荡（准二维晶体）的平面的方向上局部移动，我们观察到与系统的周期性共存的有限超流密度的出现。
英文摘要：
In a recent study we have reported a new type of trial wave function symmetric under the exchange of particles and which is able to describe a supersolid phase. In this work, we use the diffusion Monte Carlo method and this model wave function to study the properties of solid 4He in two- and quasi two-dimensional geometries. In the purely two-dimensional case, we obtain results for the total ground-state energy and freezing and melting densities which are in good agreement with previous exact Monte Carlo calculations performed with a slightly different interatomic potential model. We calculate the value of the zero-temperature superfluid fraction ρ_{s} / ρof 2D solid 4He and find that it is negligible in all the considered cases, similarly to what is obtained in the perfect (free of defects) three-dimensional crystal using the same computational approach. Interestingly, by allowing the atoms to move locally in the perpendicular direction to the plane where they are confined to zero-point oscillations (quasi two-dimensional crystal) we observe the emergence of a finite superfluid density that coexists with the periodicity of the system.
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