Will cold atomic systems help us to understand high-Tc superconductivity?

Description
The understanding of high-temperature superconductors represents one of the major challenges in condensed matter physics. Despite 25 years of intensive efforts, the answer is not yet there. During the last years, cold atoms loaded into optical lattices emerged as an ideal playground to emulate condensed matter systems. In this talk, I will show that by studying a mixture of bosons and two-species fermions in an optical lattice in the presence of an artificial staggered gauge field, several features of the high-Tc phase diagram can be reproduced. Starting from a DDW phase, with a staggered pi-flux traversing each plaquette, unconventional superconductivity with features of the RVB state is obtained for a certain range of parameters. Even more interestingly, the complexity of the normal phase surrounding the superconducting dome emerges naturally in this system, and the evolution from a non-Fermi liquid to a Fermi-liquid behavior with increasing doping can be clearly understood. The evolution of the Fermi-surface upon doping also shows that CDW and SDW instabilities could easily occur, due to nesting. Our work suggests that probably a generalized Hubbard model, with a complex hopping parameter, should be more appropriate to describe high-temperature superconductors than the usual Hubbard model. References: Lih-King Lim, A. Lazarides, A. Hemmerich, and C. Morais Smith, EPL 88, 36001 (2009). Lih-King Lim, C. Morais Smith, and A. Hemmerich, PRL 100, 130402 (2008). A. Hemmerich and C. Morais Smith, PRL 99, 113002 (2007).
Organised by Vincenzo Branchina