Spin and charge density waves in the Lieb lattice

Abstract

We study the mean-field phase diagram of the two-dimensional (2D) Hubbard model in the Lieb lattice allowing for spin and charge density waves. Previous studies of this diagram have shown that the mean-field magnetization surprisingly deviates from the value predicted by Lieb's theorem \cite{Lieb1989} as the on-site repulsive Coulomb interaction ($U$) becomes smaller \cite{Gouveia2015}. Here, we show that in order for Lieb's theorem to be satisfied, a more complex mean-field approach should be followed in the case of bipartite lattices or other lattices whose unit cells contain more than two types of atoms. In the case of the Lieb lattice, we show that, by allowing the system to modulate the magnetization and charge density between sublattices, the difference in the absolute values of the magnetization of the sublattices, $m_{\text{Lieb}}$, at half-filling, saturates at the exact value $1/2$ for any value of $U$, as predicted by Lieb. Additionally, Lieb's relation, $m_{\text{Lieb}}=1/2$, is verified approximately for large $U$, in the $n\in [2/3,4/3]$ range. This range includes not only the ferromagnetic region of the phase diagram of the Lieb lattice (see Ref.~\onlinecite{Gouveia2015}), but also the adjacent spiral regions. In fact, in this lattice, below or at half-filling, $m_{\text{Lieb}}$ is simply the filling of the quasi-flat bands in the mean-field energy dispersion both for large and small $U$.

References in corpus (5)

• Topological Phases for Fermionic Cold Atoms on the Lieb Lattice
• Dynamical Mean Field Study of the Two-Dimensional Disordered Hubbard Model
• Flat-band ferromagnetism in the multilayer Lieb optical lattice
• Magnetic phase diagram of the Hubbard model in the Lieb lattice
• Attractive Hubbard model with disorder and the generalized Anderson theorem

Cited by in corpus (6)

• Strain induced superconductor-insulator transition on Lieb lattice
• Impact of strong correlations on a band topological insulator on the Lieb lattice
• Generalized Lieb's theorem for noninteracting non-Hermitian $n$-partite tight-binding lattices
• Metal-insulator transition in the disordered Hubbard model of the Lieb lattice
• Ground state spin and excitation energies in half-filled Lieb lattices
• Canted magnetism and ${\mathbb{Z}}_2$ fractionalization in metallic states of the Lieb lattice Hubbard model near quarter filling