Group seminar at MPQ and Zoom: Exploring quantum many-body physics in the 2D dipolar superfluid

Yifei He, Rice/Hong-Kong University of Science and Technology
Group seminar at MPQ lecture hall and Zoom
Thursday, 13 November, 09:00am (MEZ)

Two-dimensional (2D) systems exhibit fundamentally distinct properties compared to their three-dimensional (3D) counterparts, as enhanced fluctuations prevent long-range order at finite temperature with only short-range interactions. However, a superfluid with quasi-long-range order can still emerge in 2D at finite temperature through the Berezinskii-Kosterlitz-Thouless (BKT) mechanism. Long-range and anisotropic dipole-dipole interactions (DDI) enable the observation of exotic phases in ultracold quantum gases like quantum droplets and supersolids, which has been extensively studied in the past decade. While theoretical studies have long predicted the emergence of complex orders in 2D dipolar Bose gases, a systematic experimental investigation of 2D dipolar superfluids has remained elusive. 

In this talk, I will present our recent experimental advances in studying a 2D dipolar superfluid of ultracold erbium atoms across a broad range of relative dipolar strengths. We study the impact of DDI on BKT transition [1] and measure the collective excitations of strongly dipolar superfluid in 2D [2]. Furthermore, by precisely tuning the interaction parameters, we observe the evidence of 2D supersolid stripe in a narrow regime of anisotropic roton instability [3]. This finding opens new avenues for exploring the interplay between BKT superfluid and supersolidity in future studies.

[1] Yifei He*, Ziting Chen* et al. Science Advances11, eadr2715 (2025)
[2] Haoting Zhen*, Yifei He* et al. arXiv:2510.13730 (2025)
[3] Yifei He et al. In preparation