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arXiv 1406.6506cond-mat.quant-gas
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声学极化子和BEC极化子的图解Monte Carlo研究

Diagrammatic Monte Carlo study of the acoustic and the BEC polaron

Jonas Vlietinck, Wim Casteels, Kris Van Houcke, Jacques Tempere, Jan Ryckebusch, Jozef T. Devreese

摘要:

我们考虑了两个用Fröhlich型哈密顿量描述的大极化子系统,即连续介质中的玻色-爱因斯坦凝聚体(BEC)极化子和固体中的声学极化子。我们提出了这两个系统的基态能量计算与Diagrammatic Monte Carlo(DiagMC)方法和费曼全耦合方法。DiagMC方法评估了非常高的阶的极化子格林函数的图解系列。费曼全耦合方法是一种变分方法,已被用于广泛的极化问题。对于声学和BEC极化子,这两种方法提供了非常相似的非重整化基态能量后,引入有限的动量截止。对于BEC极化子的重整化基态能量,DiagMC和Feynman的预测之间存在较大的差异。这些差异可以归因于接触相互作用的重整化过程。

英文摘要:

We consider two large polaron systems that are described by a Fröhlich type of Hamiltonian, namely the Bose-Einstein condensate (BEC) polaron in the continuum and the acoustic polaron in a solid. We present ground-state energies of these two systems calculated with the Diagrammatic Monte Carlo (DiagMC) method and with a Feynman all-coupling approach. The DiagMC method evaluates up to very high order a diagrammatic series for the polaron Green's function. The Feynman all-coupling approach is a variational method that has been used for a wide range of polaronic problems. For the acoustic and BEC polaron both methods provide remarkably similar non-renormalized ground-state energies that are obtained after introducing a finite momentum cutoff. For the renormalized ground-state energies of the BEC polaron, there are relatively large discrepancies between the DiagMC and the Feynman predictions. These differences can be attributed to the renormalization procedure for the contact interaction.

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