Fermionic superfluids in two and three dimensions

Understanding the origins of unconventional superconductivity has been a major focus of condensed matter physics for many decades. While many questions remain unanswered, experiments have found the highest critical temperatures in layered two-dimensional materials. However, to what extent the remarkable stability of these strongly correlated 2D superfluids is affected by their reduced dimensionality is still an open question. Here, I will review our work studying superfluidity in homogeneous 2D and 3D Fermi gases, in particular measurements of the dynamic structure factor of 2D [1,2] and 3D [3] superfluids. Using Bragg spectroscopy, we determine the critical velocity and the superfluid gap in the BEC-BCS crossover, allowing for detailed comparisons with and benchmarks for theory. Our measurements enable us to directly study the role of reduced dimensionality on strongly correlated superfluids [2].

In the outlook I will report on our ongoing investigation of spin-imbalanced 2D Fermi gases.

[1] L. Sobirey et al., Science 372, 844 (2021)

[2] L. Sobirey et al., PRL 129, 083601 (2022)

[3] H. Biss et al., PRL 128, 100401 (2022)