Heavy-light fermion mixtures at unitarity.

Area of Science:

• Ultracold atomic physics
• Quantum many-body systems
• Fermionic superfluidity

Background:

• Investigating fermion pairing is crucial for understanding quantum phenomena.
• The unitary regime offers a unique platform for studying strongly interacting Fermi gases.
• Mass-imbalanced Fermi mixtures present complex phase diagrams.

Purpose of the Study:

• To investigate fermion pairing in a mass-imbalanced {6}Li-{40}K mixture at unitarity.
• To determine the ground-state energy and excitation spectrum for different particle ratios.
• To explore phase separation phenomena in polarized and unpolarized superfluids.

Main Methods:

• Utilizing quantum Monte Carlo (QMC) methods for high-precision calculations.
• Simulating the unitary Fermi gas with a specific mass ratio.
• Analyzing ground-state energy and excitation spectra.

Main Results:

• Ground-state energy and excitation spectra are largely independent of mass ratio in the unpolarized state.
• Majority light systems exhibit polarized superfluids near phase-separated mixtures.
• Majority heavy systems show an energy minimum for a 3:1 heavy-to-light normal state at unitarity.
• Near-universal attraction (kFa ≈ 2.5) leads to near-zero ground state energy for the 3:1 ratio.

Conclusions:

• The mass ratio has a limited impact on unpolarized superfluid properties.
• Polarization and mass imbalance drive significant phase separation behaviors.
• Harmonically trapped, cold, unpolarized systems at unitarity are predicted to exhibit three distinct regions with a superfluid core.