液氦量子效应的路径积分蒙特卡罗模拟

Simulation of quantum effects in liquid helium using path integral Monte Carlo

摘要:

为研究液氦中的量子效应,采用路径积分蒙特卡罗(PIMC)的方法对液氦体系进行模拟.在pimc++的平台上计算了体系中发生交换的原子数、对关联函数、结构因子以及超流分数等物理量.模拟的结果表明:对关联函数以及结构因子的值与实验数据符合得很好,PIMC可以对液氦中原子的微观排布进行精确的模拟.在4K的范围内,随着温度的降低,发生交换的粒子数目越来越多,体系的量子效应越来越明显.温度在临界温度2.17K左右的时候,体系出现超流,超流分数随着温度的降低而升高.路径积分蒙特卡罗可以精确地模拟液氦的结构,并且反映出全同粒子交换和超流相变等量子效应.

Abstract:

In order to study the quantum effects in the liquid helium,we use path integral Monte Carlo(PIMC) method to simulate the liquid helium system.We calculate the number of atoms which permute with others,the pair-correlation function,the structure factor and the superfluid fraction on the platform of pimc++.Comparison between experiments and the results of pair-correlation and structure factor computed by PIMC manifests the precision of this method and the strength of this approach in simulating the microscopic arrangement of atoms in liquid helium.Below 4K,the number of atoms which permute with others increases as the temperature goes down,the quantum effects become more and more apparent.At about 2.17 K,the system will undergo a phase transition and turn into superfluid.The superfluid fraction will increase as the temperature goes down,and eventually equals to 1.Path integral Monte Carlo can simulate the structure of liquid helium with high precision and reflect the quantum effects of particle permutation and transition to the superfluid state.