标题： 二维氦-4的相图和晶体熔化 显示英文标题

标题： Phase diagram and crystal melting of helium-4 in two dimensions

摘要： 我们使用神经量子态研究二维氦-4的零温相图。 我们的变分描述使我们能够使用相同的函数形式来处理液相和固相，并探索可能的熔化情景，例如通过中间的六角相。 值得注意的是，这是通过进行固定压力的变分蒙特卡罗计算实现的。 在等压系综框架下，我们能够明确识别一阶液-固相变。 然而，在接近恒定压力的中间区域，我们发现模拟的$N=30$个原子连续地从液相过渡到固相，表现出六角序与少量凝聚态分数共存的特征。 更大系统的计算在此瞬态区域中遵循亚稳液相和固相分支。 我们还计算了液-固相变过程中的Rényi-2纠缠熵，并发现冻结时出现急剧下降。 显示英文摘要

摘要： We study the zero-temperature phase diagram of two-dimensional helium-4 using neural quantum states. Our variational description allows us to address liquid and solid phases using the same functional form as well as exploring possible melting scenarios, for instance via an intermediate hexatic phase. Notably, this is achieved by performing fixed pressure variational Monte Carlo calculations. Within the isobaric ensemble framework, we are able to clearly identify the first-order liquid-solid phase transition. However, in an intermediate region of nearly constant pressure, we find that simulations of $N=30$ atoms continuously transition from liquid to solid, with signatures of a hexatic order coexisting with a small condensate fraction. Calculations for larger systems follow the metastable liquid and solid branches in this transient region. We additionally compute the R\'enyi-2 entanglement entropy across the liquid-solid phase transition and find a sharp decrease upon freezing.