Atom-resolved microscopy of exotic superfluids in spin-imbalanced Fermi gases

非技术性：超导体是一种电流无损耗的材料，在制造强大的电磁铁、敏感的磁场传感器和磁悬浮设备方面有着重要的应用。了解超导体在磁场中的行为对于建造更好的超导设备至关重要。虽然强磁场通常会抑制超导电性，但在适当的条件下，它们也被预测会导致物质的奇异超导相。五十多年前就提出了这样一个相，但从未在任何材料中被直接观察到。这项研究的目的是在冷却到极低温度的原子气体中发现这种物质相。在教育方面，该项目对本科生、研究生和博士后研究员进行超冷气体技术培训。为了补充实验工作，首席研究人员正在开发和教授一门关于超冷原子物理的研究生课程，重点是实验技术和潜在的应用。这门课程旨在通过客座讲座的机会，培训PI实验室的研究生进行教学。技术：超导和磁性之间的竞争可能会产生量子物质的奇异相。五十多年前，Fulde、Ferrell、Larkin和Ovchinnikov(FFLO)预测了超导体在磁场中的库珀对以非零动量凝聚的量子相。有间接证据表明，在层状有机超导体、重费米子材料和超冷原子气体中存在这种相，但对其定义特征的直接检测一直难以捉摸。这个项目的目标是直接探测自旋不平衡的超流原子费米气体中的FFLO相。研究小组使用原子分辨的气体原位成像来寻找它的确凿证据：磁化和超流体间隙的空间振荡取决于气体的极化。该相的寻找是在低维晶格系统中进行的，其中预测了费米面嵌套效应以增强FFLO相占据的相图区域。该团队试图了解自旋不平衡的二维费米气体的低温相图，使用量子气体显微镜通过其磁化强度和局域态密度的急剧变化来成像印迹孤子晶格，并应用这些成像技术来搜索处于热平衡状态的FFLO。

Non-technical:Superconductors, materials that have electrical currents that flow without losses, have important applications in building powerful electromagnets, sensitive sensors of magnetic fields and magnetic levitation devices. Understanding the behavior of superconductors in magnetic fields is crucial to building better superconducting devices. While large magnetic fields usually suppress superconductivity, they have also been predicted to lead to exotic superconducting phases of matter under the proper conditions. One such phase was proposed over fifty years ago, but has never been directly observed in any material. This research effort aims to discover this phase of matter in a gas of atoms cooled to very low temperatures. On the educational side, the project trains undergraduates, graduate students and a post-doctoral researcher in the techniques of ultracold gases. To complement the experimental effort, the principal investigator is developing and teaching a graduate course in ultracold atom physics, focusing on experimental techniques and potential applications. The course serves to train graduate students from the PI's lab in teaching through guest lecture opportunities. Technical:The competition between superconductivity and magnetism can give rise to exotic phases of quantum matter. Over fifty years ago, Fulde, Ferrell, Larkin and Ovchinnikov (FFLO) predicted a quantum phase where the Cooper pairs of a superconductor in a magnetic field condense at non-zero momentum. There has been indirect evidence for the existence of this phase in layered organic superconductors, heavy fermion materials and ultracold atomic gases, but a direct detection of its defining signatures has been elusive. The goal of this project is the direct detection of the FFLO phase in a superfluid atomic Fermi gas with spin imbalance. The research team uses atom-resolved in-situ imaging of the gas to search for its smoking gun signature: a spatial oscillation of the magnetization and superfluid gap that depends on the polarization of the gas. The search for this phase is conducted in a lower-dimensional lattice system where Fermi surface nesting effects are predicted to enhance the region of the phase diagram occupied by the FFLO phase. The team seeks to understand the low-temperature phase diagram of spin-imbalanced two-dimensional Fermi gases, use quantum gas microscopy to image imprinted solitonic lattices through the sharp variation of their magnetization and local density of states and apply these imaging techniques to search for FFLO in a thermal equilibrium state.