Effect of Spin-Selective Disorder on the Hubbard model.

We use a combination of Monte-Carlo techniques to study the effect of spin-selective disorder for both the repulsive and attractive Hubbard models. For the repulsive Hubbard model with spin-selective disorder, by using a determinant quantum Monte-Carlo scheme we show evidence for the existence of a metal-insulator transition for fillings away from half-fillings. We show that the metal-insulator transition is accompanied with a net-polarization of the fermionic fluid and a consequent saturation behavior in the susceptibility. For the case of the attractive Hubbard model at half-filling in the presence of spin-selective disorder, we use a real space based Monte-Carlo scheme to completely elucidate the ground state phase diagram. In particular, we compare and contrast the behavior at weak and strong disorder: In the limit of weak disorder gapless superconductivity obtains whereas in the limit of strong disorder a spin-selective Anderson transition is realized. The effect of thermal fluctuations on the phase diagram is also studied within this approach.