Fermi-Fermi quantum many-body systems in optical lattices

超冷费米子原子自旋混合为费米子强相互作用量子多体系统中的关键现象如费米子对和费米超流体等提供了独特的模型系统。到目前为止，大多数实验都是基于相同费米子种的自旋混合物，尽管实验已经开始研究新的自由度——比如自旋不平衡——以探索新的超流体相。在本研究项目中，我们计划实现并实验建立两种不同费米子原子种的混合物作为新型量子多体系统。这方面的关键目标是阐明质量差对费米子量子系统中的配对现象和超流体性质的作用。不匹配的费米表面有望导致新的量子相，如FFLO （Fulde-Ferrell-Larkin-Ovchinnikov）相和破缺对超流动性。预计重原子和轻原子的弱结合二聚体通过交换轻原子而相互强烈作用。这甚至可以导致大质量比的结晶相的形成。从少体的观点来看，考虑到叶菲莫夫物理学和长寿命三聚体态的可能性，质量不平衡费米子混合物是特别有趣的。在新装置的基础上，本研究项目将重点研究费米子6Li和40K原子在三维光学晶格中的量子简并两种混合物。我们将开发将两种不同的费米子种装入光学晶格的技术，以获得对晶格中费米子填充因子的精确控制-这是基于晶格的实验的基本控制参数。再加上基于费什巴赫共振的相互作用的可调性和两个费米子种之间有效质量比的可调性，这将使我们能够在光学晶格中设计出各种各样的量子相。我们的目标是研究这种质量平衡混合物中的量子相，这些量子相主要是在质量平衡费米-哈伯德模型中描述的，例如带和莫特绝缘体相，磁有序相和超流体相。该实验项目将与T1 （U. Schollwöck）、T2 （W. Hofstetter）和T3 （W. Zwerger）计划的理论工作直接相关，它将补充E1 （I. Bloch）和E2 （K. Sengstock）中进行的费米-费米混合物的实验研究，以及E3 （K. Dieckmann）中进行的均匀费米-费米混合物的研究。

Spin mixtures of ultracold fermionic atoms have provided a unique model system for key phenomena in fermionic strongly interacting quantum many-body systems such as Fermion pairing and Fermi superfluidity. So far, the majority of the experiments have been based on spin mixtures of the same fermionic species, although experiments have started to investigate new degrees of freedom - such as spin imbalance - to explore novel superfluid phases.In this research project, we plan to realize and experimentally establish mixtures of two different fermionic atomic species as novel quantum many-body systems. Key goals in this context are to elucidate the role of mass difference on pairing phenomena and superfluid properties in fermionic quantum systems. Unmatched Fermi surfaces are expected to lead to novel quantum phases such as the FFLO (Fulde-Ferrell-Larkin-Ovchinnikov) phase and breached pair superfluidity. Weakly bound dimers of heavy and light atoms are predicted to strongly interact with each other by exchanging light atoms. This can even lead to the formation of a crystalline phase for large mass ratio. From the few-body point of view, mass-imbalanced fermionic mixtures are of particular interest in view of Efimov physics and the possibility of long-lived trimer states.Based on the setup of a new apparatus, the work within this research project will focus on the investigation of quantum degenerate two-species mixtures of fermionic 6Li and 40K atoms in three dimensional optical lattices. We will develop techniques to load two different fermionic species into optical lattices to gain precise control over the filling factor of fermions in the lattice – an essential control parameter for lattice based experiments. Together with tunability of interactions based on Feshbach resonances and the tunability of the effective mass ratio between the two fermionic species, this will allow us to engineer a wide variety of quantum phases in the optical lattice. Our goal is to study the quantum phases in such a massimbalanced mixture which are mainly described within the Fermi-Hubbard model for a massimbalanced fermionic mixture, e.g. band and Mott insulators phases, magnetically ordered phases and superfluid phases. This experimental project will be directly related to theoretical work planned in T1 (U. Schollwöck), T2 (W. Hofstetter), and T3 (W. Zwerger), it will be complementary to the experimental studies on Fermi-Bose mixtures performed within E1 (I. Bloch) and E2 (K. Sengstock), and the study of homogeneous Fermi-Fermi mixtures within E3 (K. Dieckmann).