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

自旋不平衡费米气体中奇异超流体的原子分辨显微镜

• 批准号: 1607277
• 负责人: Waseem Bakr
• 金额: $ 47.66万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1607277&HistoricalAwards=false
• 关键词: Atom; resolved; microscopy; exotic; superfluids

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.

非技术性：超导体是一种电流可以无损耗流动的材料，在构建强大的电磁体、灵敏的磁场传感器和磁悬浮装置方面具有重要的应用。了解超导体在磁场中的行为对于构建更好的超导设备至关重要。虽然大磁场通常会抑制超导性，但人们也预测它们在适当的条件下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直接观察到。这项研究工作旨在发现冷却至极低温度的原子气体中的物质相。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，首席研究员正在开发和教授超冷原子物理学研究生课程，重点关注实验技术和潜在应用。该课程旨在通过客座讲座机会对 PI 实验室的研究生进行教学培训。技术：超导性和磁性之间的竞争会产生量子物质的奇异相。五十多年前，富尔德、费雷尔、拉金和奥夫钦尼科夫 (FFLO) 预测了一个量子相，其中磁场中超导体的库珀对以非零动量凝聚。有间接证据表明该相存在于层状有机超导体、重费米子材料和超冷原子气体中，但对其定义特征的直接检测一直难以实现。该项目的目标是直接检测具有自旋不平衡的超流原子费米气体中的 FFLO 相。研究小组利用气体的原子分辨原位成像来寻找其确凿证据：取决于气体极化的磁化强度和超流体间隙的空间振荡。对该相的搜索是在低维晶格系统中进行的，其中预测费米表面嵌套效应会增强 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部状态密度的急剧变化对印迹孤子晶格进行成像，并应用这些成像技术来寻找FFLO处于热平衡状态。