Antiferromagnetism of Repulsively Interacting Fermions in a Harmonic Trap

Niels Jakob Søe Loft, Amin S. Dehkharghani, Nirav P. Mehta +2 more

M. L. Glasser, Norman Henry March, Luis Miguel Nieto

Qi Jian-Qing, Wang Lei, Xi Dai

We propose a real-space Gutzwiller variational approach and apply it to a system of repulsively interacting ultracold fermions with spin-½ trapped in an optical lattice with a harmonic confinement. Using the real-space Gutzwiller variational approach, we find that in a system with balanced spin-mixtures on a square lattice, antiferromagnetism either appears in a checkerboard pattern or forms a ring, and the antiferromagnetic order is stable in the regions where the particle density is close to one, which is consistent with the recent results obtained by the real-space dynamical mean-field theory approach. We also investigate the imbalanced case and find that the antiferromagnetic order is suppressed there.

A. N. Das, S. Sil

J. R. Armstrong, Massimo Rontani, Sven AAberg +2 more

Thereza Paiva, Yen Lee Loh, Mohit Randeria +2 more

A major challenge in realizing antiferromagnetic and superfluid phases in optical lattices is the ability to cool fermions. We determine the equation of state for the 3D repulsive Fermi-Hubbard model as a function of the chemical potential, temperature, and repulsion using unbiased determinantal quantum Monte Carlo methods, and we then use the local density approximation to model a harmonic trap. We show that increasing repulsion leads to cooling but only in a trap, due to the redistribution of entropy from the center to the metallic wings. Thus, even when the average entropy per particle is larger than that required for antiferromagnetism in the homogeneous system, the trap enables the formation of an antiferromagnetic Mott phase.