Thermography of the superfluid transition in a strongly interacting Fermi gas

• DOI: 10.1126/science.adg3430
• Publication Date: 2024-02-08T19:01:35Z
• Authors: Zhenjie Yan; Parth B. Patel; Biswaroop Mukherjee; Chris J. Vale; Richard J. Fletcher; Martin W. Zwierlein
• Keywords: Superconductivity (cond-mat.supr-con); Condensed Matter - Strongly Correlated Electrons; 0303 health sciences; 03 medical and health sciences; Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); Quantum Gases (cond-mat.quant-gas); Condensed Matter - Superconductivity; FOS: Physical sciences; Condensed Matter - Quantum Gases; 7. Clean energy; Condensed Matter - Statistical Mechanics

Heat transport can serve as a fingerprint identifying different states of matter. In a normal liquid, a hotspot diffuses, whereas in a superfluid, heat propagates as a wave called “second sound.” Direct imaging of heat transport is challenging, and one usually resorts to detecting secondary effects. In this study, we establish thermography of a strongly interacting atomic Fermi gas, whose radio-frequency spectrum provides spatially resolved thermometry with subnanokelvin resolution. The superfluid phase transition was directly observed as the sudden change from thermal diffusion to second-sound propagation and is accompanied by a peak in the second-sound diffusivity. This method yields the full heat and density response of the strongly interacting Fermi gas and therefore all defining properties of Landau’s two-fluid hydrodynamics.