| Description: | [DPS seminar] Yogeshwar Prasad (IISc, Bangalore) -- Study of fermionic superfluid state in ``clean'' and ``dirty'' bilayer system circumventing the ``cooling problem'' in optical lattices. |
| Date: | Wednesday, May 17, 2017 |
| Time: | 2 p.m. - 3 p.m. |
| Venue: | G08, Lecture Hall Complex |
| Details: | The advancement in the field of cold atoms has seen a roadblock for fermions in optical lattices due to the cooling problem or 'entropy removal issues'. To circumvent the cooling problem for fermions in optical lattice systems we propose a model whose idea hinges on a low-entropy band-insulator state, which can be tuned to superfluid state by tuning the on-site attractive interaction by Feshbach resonance. We show through Gaussian fluctuation theory that the critical temperature that can be achieved is much higher in our model as compared to the single-band Hubbard model. Through detailed variational Monte Carlo calculations, we have shown that the superfluid state is indeed the most stable ground state and there is no other competing order. In the end we give a proposal for its realization in the optical lattice experiments. Through determinant quantum Monte-Carlo simulations we studied various single-particle properties which can be easily measured in the cold-atom experiments. We performed a detailed analysis of the pair and density correlations and mapped out the full $T-U$ phase diagram. We have studied the effect of on-site random disorder in our system and see the suppression of the pair correlations as we increase the disorder strength. We find that the critical value of the interaction doesn't change in the weak-disorder limit. We estimated the critical disorder strength needed to destroy the superfluid state and argued that the transition from the superfluid to Bose-glass phase in presence of disorder lies in the universality class of (d+1)-XY model. |
| Calendar: | Seminar Calendar (entered by anandamohan) |