近日，美国哈佛大学的Jonas von Milczewski与德国海德堡大学的Richard Schmidt合作并取得一项新进展。经过不懈努力，他们从泛函重整化群揭示费米极化子动量依赖的准粒子性质。相关研究成果已于2024年9月9日在国际知名学术期刊《物理评论A》上发表。

该研究团队从理论上研究了三维空间中吸引型和排斥型费米极化子的寿命，以及有限动量下的分子寿命。为此，研究人员开发了一种技术，该技术能够在泛函重整化群框架内，通过精确的解析延拓，计算整个复频率平面上的格林函数。

该方法提高了数值稳定性并降低了计算成本，从而能够访问以往难以获取的低激发态的动量依赖准粒子特性。传统的非自洽T矩阵近似方法等方法无法确定这些寿命，而研究人员能够找出不同相互作用强度下，吸引型和排斥型极化子以及分子的动量依赖寿命。

在弱耦合情况下，这项研究结果证实了有效费米液体理论关于吸引型极化子衰变的预测，并且研究人员证明了费米液体类似行为延伸至强耦合区域，在该区域内，吸引型极化子和分子的衰变宽度呈现出p⁴的动量标度。这项研究结果为费米极化子问题的动量依赖准粒子特性提供了有趣的见解，这些特性可以通过诸如拉曼转移和拉姆齐干涉测量等技术进行测量。

附：英文原文

Title: Momentum-dependent quasiparticle properties of the Fermi polaron from the functional renormalization group

Author: Jonas von Milczewski, Richard Schmidt

Issue&Volume: 2024/09/09

Abstract: We study theoretically the lifetimes of attractive and repulsive Fermi polarons, as well as the molecule at finite momentum in three dimensions. To this end, we develop a technique that allows for the computation of Green's functions in the whole complex frequency plane using exact analytical continuation within the functional renormalization group. The improved numerical stability and reduced computational cost of this method yield access to previously inaccessible momentum-dependent quasiparticle properties of low-lying excited states. While conventional approaches like the non-self-consistent -matrix approximation method cannot determine these lifetimes, we are able to find the momentum-dependent lifetime at different interaction strengths of both the attractive and repulsive polaron as well as the molecule. At weak coupling our results confirm predictions made from effective Fermi liquid theory regarding the decay of the attractive polaron, and we demonstrate that Fermi liquidlike behavior extends far into the strong-coupling regime where the attractive polaron and molecule exhibit a p⁴ momentum scaling in their decay widths. Our results offer an intriguing insight into the momentum-dependent quasiparticle properties of the Fermi polaron problem, which can be measured using techniques such as Raman transfer and Ramsey interferometry.

DOI: 10.1103/PhysRevA.110.033309

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.033309