Fermionic atoms in a three dimensional optical lattice: observing Fermi surfaces, dynamics, and interactions

Area of Science:

• Quantum physics
• Atomic physics
• Condensed matter physics

Background:

• Quantum degenerate Fermi gases are fundamental systems for studying many-body physics.
• Optical lattices provide a controllable environment to simulate condensed matter phenomena.

Purpose of the Study:

• To investigate the properties of interacting and noninteracting quantum degenerate Fermi gases in a 3D optical lattice.
• To directly image the Fermi surface and study transitions between normal and band insulator states.

Main Methods:

• Adiabatic imaging of the Fermi surface by adiabatically turning off the optical lattice.
• Utilizing Feshbach resonance to control interatomic interactions.
• Dynamically inducing coupling between the lowest energy bands.

Main Results:

• Observed the transformation from a normal state to a band insulator due to confining potential and lattice filling.
• Measured the transition dynamics from band insulator to normal state, finding a timescale an order of magnitude larger than tunneling time.
• Observed a shift in the induced band coupling relative to the Feshbach resonance in free space for strongly confined atoms.

Conclusions:

• The study provides direct imaging and dynamic insights into Fermi gases in optical lattices.
• The observed shift in band coupling is consistent with theoretical predictions for strongly confined systems.
• This work advances the understanding of quantum phase transitions and interactions in ultracold atomic gases.