Since the achievement of quantum degeneracy in gases of chromium atoms in 2004, the experimental investigation of ultracold gases made of highly magnetic atoms has blossomed. The field has yielded the observation of many unprecedented phenomena, in particular those in which long-range and anisotropic dipole–dipole interactions (DDIs) play a crucial role. In this review, we aim to present the aspects of the magnetic quantum-gas platform that make it unique for exploring ultracold and quantum physics as well as to give a thorough overview of experimental achievements. Highly magnetic atoms distinguish themselves by the fact that their electronic ground-state configuration possesses a large electronic total angular momentum. This results in a large magnetic moment and a rich electronic transition spectrum. Such transitions are useful for cooling, trapping, and manipulating these atoms. The complex atomic structure and large dipolar moments of these atoms also lead to a dense spectrum of resonances in their two-body scattering behaviour. These resonances can be used to control the interatomic interactions and, in particular, the relative importance of contact over dipolar interactions. These features provide exquisite control knobs for exploring the few- and many-body physics of dipolar quantum gases. The study of dipolar effects in magnetic quantum gases has covered various few-body phenomena that are based on elastic and inelastic anisotropic scattering. Various many-body effects have also been demonstrated. These affect both the shape, stability, dynamics, and excitations of fully polarised repulsive Bose or Fermi gases. Beyond the mean-field instability, strong dipolar interactions competing with slightly weaker contact interactions between magnetic bosons yield new quantum-stabilised states, among which are self-bound droplets, droplet assemblies, and supersolids. Dipolar interactions also deeply affect the physics of atomic gases with an internal degree of freedom as these interactions intrinsically couple spin and atomic motion. Finally, long-range dipolar interactions can stabilise strongly correlated excited states of 1D gases and also impact the physics of lattice-confined systems, both at the spin-polarised level (Hubbard models with off-site interactions) and at the spinful level (XYZ models). In the present manuscript, we aim to provide an extensive overview of the various related experimental achievements up to the present.

中文翻译：

---

偶极物理学：磁性量子气体实验综述

自 2004 年实现铬原子气体的量子简并以来，由高磁性原子构成的超冷气体的实验研究蓬勃发展。该领域已经观察到许多前所未有的现象，特别是那些长程和各向异性偶极-偶极相互作用 (DDI) 发挥关键作用的现象。在这篇综述中，我们旨在介绍磁性量子气体平台的各个方面，使其在探索超冷和量子物理方面独树一帜，并全面概述实验成果。高磁性原子因其电子基态构型具有较大的电子总角动量而与众不同。这导致大磁矩和丰富的电子跃迁谱。这种转变对冷却很有用，捕获和操纵这些原子。这些原子的复杂原子结构和大偶极矩也导致它们的双体散射行为中出现密集的共振光谱。这些共振可用于控制原子间相互作用，特别是控制接触相对于偶极相互作用的相对重要性。这些功能为探索偶极量子气体的少体和多体物理学提供了精致的控制旋钮。磁量子气体中偶极效应的研究涵盖了基于弹性和非弹性各向异性散射的各种少体现象。还证明了各种多体效应。这些影响完全极化排斥玻色或费米气体的形状、稳定性、动力学和激发。除了平均场不稳定性，强偶极相互作用与磁性玻色子之间稍弱的接触相互作用产生新的量子稳定态，其中包括自束缚液滴、液滴组装和超固体。偶极相互作用也深刻影响具有内部自由度的原子气体的物理学，因为这些相互作用本质上耦合自旋和原子运动。最后，长程偶极相互作用可以稳定一维气体的强相关激发态，也可以影响晶格限制系统的物理特性，无论是在自旋极化水平（具有场外相互作用的哈伯德模型）​​还是在自旋水平（XYZ楷模）。在本手稿中，我们的目标是对迄今为止的各种相关实验成果进行广泛的概述。