Fermionic atoms trapped in one-dimensional optical superlattice with harmonic confinement

TL;DR

This study investigates the ground-state phases of spin-1/2 fermionic atoms in a one-dimensional optical superlattice with harmonic confinement, revealing coexistence of various insulating regimes using the density matrix renormalization group method.

Contribution

It introduces an analysis of insulating regimes in a superlattice with harmonic confinement, highlighting coexistence phenomena not seen in standard Hubbard models.

Findings

Multiple insulating regimes coexist even with non-integer atom filling.

Distinct phase characteristics are identified through density and spin correlation profiles.

Contrasts with the behavior of the ordinary Hubbard model in optical lattices.

Abstract

We study the ground-state properties of spin-1/2 fermionic atoms confined in a one-dimensional optical superlattice with harmonic confinement by using the density matrix renormalization group method. For this purpose, we consider an ionic Hubbard model that has superlattice potentials with 2-site periodicity. We find that several different types of insulating regimes coexist even if the number of atoms at each site is not an integer, but its average within the unit cell is an integer or half integer. This is contrasted to the coexisting phase of the metallic and Mott-insulating regimes known for the ordinary Hubbard model in an optical lattice. The phase characteristics are elucidated by investigating the profiles of the atom density, the local density/spin fluctuations, the double occupation probability and the spin correlations in detail.