Strongly Interacting Mass Imbalanced Superfluid with ultracold fermions

ended

Superfluids violate our classical intuition, provoking many intriguing questions in modern condensed matter physics. In particular, superfluid phases with non-standard pairing mechanisms, which play an essential role in diverse physical systems including high-Tc superconductivity, have attracted great interests, and the underlying principles challenge our understanding. Ultracold atomic systems have emerged as an ideal testbed for simulating such many-body states by directly comparing theories with experiments. Recently, the host group has achieved a novel mass-imbalanced Fermi-Fermi mixture, which offers unprecedented opportunities to realize unusual superfluid phases. Here, we propose experimental studies on unconventional superfluidity by exploiting the excellent controllability in our new quantum system. Mass imbalance changes how the two Fermi surfaces overlap, causing the pairs to have finite momentum and resulting in a rich phase diagram. We aim to explore many-body phases appearing in a mass-imbalanced Fermi-Fermi mixture near the strongly interacting limit. To demonstrate superfluidity, we will probe the atoms by magnetic and optic methods, which allow distinguishing between pairs and unpaired atoms. Moreover, we will investigate the superfluid shell structure in a trapped system to characterize the phase diagram and the thermodynamic properties in the strongly interacting regime, based on tomographic imaging. Finally, we plan to extend our methods to search for exotic forms of superfluidity such as supersolid or gapless phases. Our research will open a new chapter of condensed-matter simulation with ultracold atoms by providing a unique platform to study unconventional superfluidity. The successful demonstration will have strong impact on the scientific community even beyond the field of quantum gases. The techniques applied in this project can be further developed to address many other interesting topics such as impurity physics and transport dynamics.