Thermometry of a deeply degenerate Fermi gas with a Bose-Einstein condensate

Abstract

We measure the temperature of a deeply degenerate Fermi gas, by using a weakly interacting sample of heavier bosonic atoms as a probe. This thermometry method relies on the thermalization between the two species and on the determination of the condensate fraction of the bosons. In our experimental implementation, a small sample of 41K atoms serves as the thermometer for a 6Li Fermi sea. We investigate the evaporative cooling of a 6Li spin mixture in a single-beam optical dipole trap and observe how the condensate fraction of the thermometry atoms depends on the final trap depth. From the condensate fraction, the temperature can be readily extracted. We show that the lowest temperature of 6.3(5)% of the Fermi temperature is obtained, when the decreasing trap depth closely approaches the Fermi energy. To understand the systematic effects that may in uence the results, we carefully investigate the role of the number of bosons and the thermalization dynamics between the two species. Our thermometry approach provides a conceptually simple, accurate, and general way to measure the temperature of deeply degenerate Fermi gases. Since the method is independent of the specific interaction conditions within the Fermi gas, it applies to both weakly and strongly interacting Fermi gases.

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• Ultrafast many-body interferometry of impurities coupled to a Fermi sea
• Thermodynamics of the BCS-BEC crossover
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• Fast, Runaway Evaporative Cooling to Bose-Einstein Condensation in Optical Traps
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• Observation of two-species vortex lattices in a mixture of mass-imbalance Bose and Fermi superfluids
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• Efficient all-optical production of large ${}^6$Li quantum gases using D${}_1$ gray-molasses cooling
• All-optical production of a degenerate mixture of 6Li and 40K and creation of heteronuclear molecules
• 1D to 3D Crossover of a Spin-Imbalanced Fermi Gas
• Simultaneous sub-Doppler laser cooling of fermionic ${}^6$Li and ${}^{40}$K on the D${}_1$ line: Theory and Experiment
• Feshbach resonances, molecular bound states and prospects of ultracold molecule formation in mixtures of ultracold K and Cs
• Collisional stability of localized Yb(${}^3{\mathrm{P}}_2$) atoms immersed in a Fermi sea of Li

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• Probing the Interface of a Phase-Separated State in a Repulsive Bose-Fermi Mixture
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• Thermometry by correlated dephasing of impurities in a 1D Fermi gas
• Observation of low-field Feshbach resonances between ${}^{161}$Dy and ${}^{40}$K
• Optically trapped Feshbach molecules of fermionic 161Dy and 40K
• Thermoelectricity of cold ions in optical lattices
• Thermodynamics and structural transition of binary atomic Bose-Fermi mixtures in box or harmonic potentials: A path-integral study
• Topological quantum thermometry
• Competing instabilities at long length scales in the one-dimensional Bose-Fermi-Hubbard model at commensurate fillings
• Probing polaron clouds by Rydberg atom spectroscopy
• Kolmogorov turbulence defeated by Anderson localization for a Bose-Einstein condensate in a Sinai-oscillator trap
• Dipole-Mode Spectrum and Hydrodynamic Crossover in a Resonantly Interacting Two-Species Fermion Mixture
• Thermoelectricity modeling with cold dipole atoms in Aubry phase of optical lattice
• Direct temperature readout in nonequilibrium quantum thermometry