T1: Rotons and quantum droplets in dipolar Bose-Einstein condensates

偶极-偶极相互作用在偶极玻色-爱因斯坦凝聚体中产生了大量新的物理学，最近的实验（特别是在项目E1和E2中）开始揭示这些物理学。最近有两个主要的主题吸引了人们的注意力：偶极旋子和量子偶极液滴。该项目将与研究股内的实验密切合作，调查这两种现象。最近在E2项目中首次创建的偶极旋子是有限动量低能激发。在这个项目中，我们将研究有限尺寸效应在物理学的旋子。此外，偶极旋子激发和量子稳定化的结合，即在E1和E2中观察到的量子液滴形成背后的机制，预计将导致丰富的基态和有限温度物理，我们也将研究。值得注意的是，这两种效应可能允许超固体的产生，其实现和性质将被分析。 量子涨落对量子稳定至关重要，在较低维度中会发生根本性的变化。我们将与项目T2一起探索二维偶极凝聚的有趣情况，这可能允许创建特别强大的量子液滴。最后，我们也将研究最近在E2中产生的二元偶极混合物的基态性质和量子涨落。

Dipole-dipole interactions lead to a wealth of new physics in dipolar Bose-Einstein condensates that recent experiments (especially in projects E1 and E2) are starting to unveil. Two main topics have recently attracted a major attention: dipolar rotons and quantum dipolar droplets. This project will investigate both phenomena, in close collaboration with experiments within the Research Unit. Dipolar rotons, recently created for the first time in project E2, are finite-momentum low-energy excitations. Within this project we will study finite-size effects in the physics of rotons. Moreover, the combination of dipolar roton excitations and quantum stabilization, i.e. the mechanism behind the formation of quantum droplets observed in E1 and E2, is expected to lead to a rich ground-state and finite-temperature physics that we will investigate as well. Remarkably, these two effects may allow for the creation of a supersolid, whose realization and properties will be analyzed. Quantum fluctuations, crucial for quantum stabilization, change radically in lower dimensions. We will explore together with project T2 the interesting case of two-dimensional dipolar condensates, which may allow for the creation of particularly robust quantum droplets. Finally, we will investigate as well the ground-state properties and quantum fluctuations of binary dipolar mixtures, recently created in E2.