2018/11/30 by Zhenjie Yan, Parth B. Patel, Biswaroop Mukherjee +3 · 2 citations
Physics and Astronomy · #cond-mat.quant-gas #cond-mat.stat-mech #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.122.093401
published as Phys. Rev. Lett. 122, 093401 (2019) · Accepted version at PRL
arxiv created 2019/01/20 · arxiv updated 2019/03/13
We study the thermal evolution of a highly spin-imbalanced, homogeneous Fermi gas with unitarity limited interactions, from a Fermi liquid of polarons at low temperatures to a classical Boltzmann gas at high temperatures. Radio-frequency spectroscopy gives access to the energy, lifetime, and short-range correlations of Fermi polarons at low temperatures T. In this regime, we observe a characteristic T2 dependence of the spectral width, corresponding to the quasiparticle decay rate expected for a Fermi liquid. At high T, the spectral width decreases again towards the scattering rate of the classical, unitary Boltzmann gas, ∝ T-1/2. In the transition region between the quantum degenerate and classical regime, the spectral width attains its maximum, on the scale of the Fermi energy, indicating the breakdown of a quasiparticle description. Density measurements in a harmonic trap directly reveal the majority dressing cloud surrounding the minority spins and yield the compressibility along with the effective mass of Fermi polarons.