2019/09/25 by Parth B. Patel, Zhenjie Yan, Biswaroop Mukherjee +3 · 1 citation
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Diffusion #Fermi Gamma-ray Space Telescope #Fermi gas #Fermion #Momentum (technical analysis) #Quantum many-body systems #Quantum oscillations #Quantum, superfluid, helium dynamics #Second sound #Superfluidity #Thermal diffusivity #Zero sound #cond-mat.quant-gas #cond-mat.stat-mech #cond-mat.str-el
paper · pdf · doi:10.1126/science.aaz5756
published as Science 370, 1222-1226 (2020)
openalex created_date 2019/09/12 · arxiv created 2019/09/25 · openalex publication_date 2020/12/04 · arxiv updated 2020/12/08 · openalex updated_date 2026/08/06
Transport of strongly interacting fermions is crucial for the properties of modern materials, nuclear fission, the merging of neutron stars, and the expansion of the early Universe. Here, we observe a universal quantum limit of diffusivity in a homogeneous, strongly interacting atomic Fermi gas by studying sound propagation and its attenuation through the coupled transport of momentum and heat. In the normal state, the sound diffusivity D monotonically decreases upon lowering the temperature, in contrast to the diverging behavior of weakly interacting Fermi liquids. Below the superfluid transition temperature, D attains a universal value set by the ratio of Planck's constant and the particle mass. Our findings inform theories of fermion transport, with relevance for hydrodynamic flow of electrons, neutrons, and quarks.