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Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving
Published on: March 30, 2017
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Exploring competing density order in the ionic Hubbard model with ultracold fermions
Michael Messer1, Rémi Desbuquois1, Thomas Uehlinger1
1Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland.
Physical Review Letters
|September 26, 2015
Summary
Researchers studied the ionic Hubbard model in a honeycomb optical lattice. They observed distinct density-ordered phases, including a charge density wave and a Mott insulating state, by analyzing atomic momentum distributions.
Area of Science:
- Quantum simulation
- Condensed matter physics
- Ultracold atomic gases
Background:
- The ionic Hubbard model is a key theoretical model for understanding strongly correlated electron systems.
- Investigating this model in tunable experimental platforms like optical lattices allows for direct observation of emergent quantum phenomena.
- Breaking inversion symmetry in lattice systems can lead to novel electronic phases.
Purpose of the Study:
- To experimentally realize and investigate the ionic Hubbard model using ultracold fermionic atoms.
- To identify and characterize distinct density-ordered phases in a honeycomb optical lattice with broken inversion symmetry.
- To probe the system's excitations and compare them with theoretical predictions.
Main Methods:
- Loading a two-component fermionic atom gas into a honeycomb optical lattice with a staggered energy offset.
- Utilizing noise correlation measurements of the atomic momentum distribution to identify density-ordered phases.
- Measuring the number of doubly occupied lattice sites to characterize local density distributions.
- Performing direction-dependent modulation spectroscopy to study system excitations.
Main Results:
- Observed a charge density wave phase for weak interactions, driven by the lattice geometry.
- Detected a Mott insulating state for strong repulsive interactions, characterized by suppressed doubly occupied sites.
- Found that the broken inversion symmetry was not apparent in the density distribution of the Mott insulating state.
- Discovered a complex excitation spectrum through modulation spectroscopy, which was compared to theoretical models.
Conclusions:
- The experimental realization provides a powerful platform for studying the ionic Hubbard model and its phases.
- The observed phases demonstrate the influence of lattice geometry and interactions on quantum many-body systems.
- The study highlights the interplay between broken symmetries and emergent electronic states in correlated systems.
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