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arXiv 1111.1861cond-mat.othercond-mat.stat-mech
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二维固体~ 4 He中的量子化涡旋

Quantized vortices in two dimensional solid 4He

M. Rossi, D. E. Galli, P. Salvestrini, L. Reatto

摘要:

采用固定相位方法,利用阴影路径积分基态方法研究了二维固体4 He量子化涡旋系统的对角和非对角性质.所选择的近似相位诱导标准Onsager-Feynman流场。在这种近似中,涡旋作为一个静态的外部势和由此产生的哈密顿量可以精确地处理与量子蒙特卡罗方法。涡核被发现坐在一个填隙网站和一个非常弱的松弛的晶格位置远离涡核的位置已被观察到。此外,其他性质,如静态结构因子中的布拉格峰或空位行为,受涡旋存在的影响很小。我们还计算了完整和有缺陷的~ 4 He晶体中的单体密度矩阵,发现涡旋对密度矩阵的非对角长程尾没有明显的影响。在假设的Onsager Feynman相位内,我们发现量子化的涡旋不能自我维持,除非已经存在像位错存在时那样的凝聚。回流是否会改变这一结论还有待研究。

英文摘要:

Diagonal and off-diagonal properties of 2D solid 4He systems doped with a quantized vortex have been investigated via the Shadow Path Integral Ground State method using the fixed-phase approach. The chosen approximate phase induces the standard Onsager-Feynman flow field. In this approximation the vortex acts as a static external potential and the resulting Hamiltonian can be treated exactly with Quantum Monte Carlo methods. The vortex core is found to sit in an interstitial site and a very weak relaxation of the lattice positions away from the vortex core position has been observed. Also other properties like Bragg peaks in the static structure factor or the behavior of vacancies are very little affected by the presence of the vortex. We have computed also the one-body density matrix in perfect and defected 4He crystals finding that the vortex has no sensible effect on the off-diagonal long range tail of the density matrix. Within the assumed Onsager Feynman phase, we find that a quantized vortex cannot auto-sustain itself unless a condensate is already present like when dislocations are present. It remains to be investigated if backflow can change this conclusion.

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