Metallic and Mott-Insulating Phases in Fermionic Quantum Gases

Martin W. Zwierlein

Immanuel Bloch, Achim Rosch

Abstract Ultracold quantum gases in optical lattices can be used as novel model system for the exploration of strongly correlated many‐body phases of bosonic or fermionic particles. Here we report on the realization of metallic, Mott‐insulating and band insulating phases in ultracold spin mixtures of fermionic 40K atoms. The experimental results are compared to ab initio dynamical mean field theory (DMFT) calculations.

W. Vincent Liu

Duong-Bo Nguyen, Minh-Tien Tran

Metal-insulator transitions are studied within a three-component Falicov-Kimball model, which mimics a mixture of one-component and two-component fermionic particles with local repulsive interactions in optical lattices. Within the model, the two-component fermionic particles are able to hop in the lattice, while the one-component fermionic particles are localized. The model is studied by using the dynamical mean-field theory with exact diagonalization. Its homogeneous solutions establish Mott transitions for both commensurate and incommensurate fillings between one-third and two-thirds. At commensurate one-third and two-thirds fillings, the Mott transition occurs for any density of hopping particles, while at incommensurate fillings, the Mott transition can occur only for density one-half of hopping particles. At half-filling, depending on the repulsive interactions, the reentrant effect of the Mott insulator is observed. As increasing local interaction of hopping particles, the first insulator-metal transition is continuous, whereas the second metal-insulator transition is discontinuous. The second metal-insulator transition crosses a finite region where both metallic and insulating phase coexist. At third-filling, the Mott transition is established only for strong repulsive interactions. A phase separation occurs together with the phase transition.

Jingyao Wang, Lufeng Zhang, Runyu Ma +3 more

By performing exact quantum Monte Carlo simulations of a model of interacting Dirac Fermions with staggered potential, we reveal a novel intermediate phase where the electronic correlations drive a band insulator metallic, and at a larger interaction, drive the metal-to-Mott insulator. We also show that the Mott insulating phase is antiferromagnetic. A complete phase diagram is achieved by studying the phase transitions at large staggered potential and interaction strengths, which shows that the intermediate state is robust and occupies a large part of the phase diagram and that it should be more feasible to be detected experimentally.

Subir Sachdev A