Matter wave probe for detecting Fermi superfluidity in trapped ultra-cold atom experiments

Alexis Bonnin, Xavier Alauze, Cyrille Solaro +4 more

Chen-Yen Lai

Ultra-cold atom system provides novel technology to simulate traditional solid state physics, including boson and fermion particles. Due to the flexibility of tuning pa- rameters, people can further understand basic physics behind strongly correlated effects, especially mechanism of unconventional density wave and superfluidity. Using weak cou- pling renormalization group method, we propose and study several models which can be realized in experiments. Ranging from most well-known extended Hubbard model, to spin- polarized Fermi Hubbard model and multi-flavor Fermi-Fermi mixture, we establish solid theories to explain the origin of new states of matter, and the experimental techniques to exploit them. The effects of lattice structure and particle density in fermionic system play important roles for determining phase diagram in low energy scale. Due to the presence of lattice, these systems have insulator phase at half-filled. The density imbalance, however, prevents formation of conventional density wave state, and the screening interaction dra- matically affects other species's behavior. The interplay between screening interaction and square lattice is key ingredient of unconventional density wave and superfluidity. Our studyvishows that the unconventional density wave and superfluidity can be realized and detected in ultra-cold atom experiments.

Satyan Bhongale, Han Pu

D. Naik

Since Feynman's realization of using quantum systems to investigate quantum dynamics, interest in creating controllable quantum systems to simulate condensed matter phenomenon has been high. With the realization of BECs in 1995, the realization of a relatively clean testbed for simulating some of these phenomenon became a reality. \n My PhD research has been an exploration of the production and use of Bose-Einstein Condensates for the study of superfluidity. The first 3 years have been spent in the actual building of a Na BEC apparatus. During this time, we’ve implemented a distinct technique to trap ultra cold Na atoms, i.e. the Optically Plugged Trap. In the process, we have shown how atoms in a linear trap can show spin metastability and thus maintain a nonequilibrium state for long periods of time.\n In studying the interaction of ultra-cold atoms with light, we have developed a technique to measure the velocity distribution of atoms using a standing optical wave (Bragg Spectroscopy). Alongside this, we have also created optical traps for atoms in which we can change to shape of the trap itself to probe different condensed matter systems. The eventual goal being the investigation of condensed matter physics, specifically superfluidity, using ultra-cold atoms.

Martin W. Zwierlein

Yi Yu, Qijin Chen