Grusdt F, Mostaan N, Demler E, Ardila L A P
Department of Physics and Arnold Sommerfeld Center for Theoretical Physics (ASC), Ludwig-Maximilians-Universität München, Theresienstr. 37, D-80333 München, Germany.
Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, D-80799 München, Germany.
Rep Prog Phys. 2025 Jun 12;88(6). doi: 10.1088/1361-6633/add94b.
This review describes the field of Bose polarons, arising when mobile impurities are immersed into a bosonic quantum gas. The latter can be realized by a Bose-Einstein condensate of ultracold atoms, or of exciton polaritons in a semiconductor, which has led to a series of experimental observations of Bose polarons near inter-species Feshbach resonances that we survey. Following an introduction to the topic, with references to its historic roots and a presentation of the Bose polaron Hamiltonian, we summarize state-of-the-art experiments. Next we provide a detailed discussion of polaron models, starting from the ubiquitous Fröhlich Hamiltonian that applies at weak couplings. Already this highly simplified model allows insights into ultra-violet divergencies, logarithmic and power-law, that need to be properly regularized. To capture the physics near a Feshbach resonance, two-phonon scattering terms on the impurity as well as phonon-phonon interactions need to be included. We proceed by a survey of concurrent theoretical methods used for solving strongly interacting Bose polaron problems, ranging from Lee-Low-Pines mean-field theory, Chevy-ansatz, Gross-Pitaevskii-equation to diagrammatic Monte Carlo approaches. The subsequent sections are devoted to the large bodies of work investigating strong coupling Bose polarons, including detailed comparisons with radio-frequency spectra obtained in ultracold atom experiments; to investigations of universal few-body and Efimov states associated with a Feshbach resonance in atomic mixtures; to studies of quantum dynamics and polarons out of equilibrium; Bose polarons in low-dimensional 1D and 2D quantum systems; induced interactions among polarons and bipolaron formation; and to Bose polarons at non-zero temperatures. We end our review by detailed discussions of closely related experimental setups and systems, including ionic impurities, systems with strong light-matter interactions, and variations and extensions of the Bose polaron concepts e.g. to baths with topological order or strong interactions relevant for correlated electrons. Finally, an outlook is presented, highlighting possible future research directions and open questions in the field as a whole.
本综述描述了玻色极化子领域，该领域产生于移动杂质浸入玻色子量子气体时。后者可通过超冷原子的玻色 - 爱因斯坦凝聚或半导体中的激子极化激元来实现，这导致了我们所综述的在种间费什巴赫共振附近对玻色极化子的一系列实验观测。在介绍该主题并提及其历史根源以及给出玻色极化子哈密顿量之后，我们总结了当前的实验进展。接下来，我们从适用于弱耦合的普遍的弗罗利希哈密顿量开始，对极化子模型进行详细讨论。即便这个高度简化的模型也能让人深入了解需要适当正则化的紫外发散、对数和幂律发散。为了捕捉费什巴赫共振附近的物理现象，需要包含杂质上的双声子散射项以及声子 - 声子相互作用。我们接着综述用于解决强相互作用玻色极化子问题的并行理论方法，范围从李 - 洛 - 派恩斯平均场理论、切维近似、格罗斯 - 皮塔耶夫斯基方程到图解蒙特卡罗方法。随后的章节致力于大量研究强耦合玻色极化子的工作，包括与超冷原子实验中获得的射频光谱的详细比较；对与原子混合物中的费什巴赫共振相关的普遍少体和埃菲莫夫态的研究；对量子动力学和非平衡极化子的研究；低维一维和二维量子系统中的玻色极化子；极化子之间的诱导相互作用和双极化子形成；以及非零温度下的玻色极化子。我们通过详细讨论密切相关的实验装置和系统来结束综述，包括离子杂质、具有强光 - 物质相互作用的系统，以及玻色极化子概念的变化和扩展，例如到具有拓扑序的浴场或与关联电子相关的强相互作用。最后，给出了展望，强调了整个领域未来可能的研究方向和未解决的问题。
