Antiferromagnetism of the Hubbard Model on a Layered Honeycomb Lattice - Is MgB${}_2$ a Nearly-Antiferromagnetic Metal? -

Abstract

As a model for the B 2pz bands of MgB${}_2$, a half-filled Hubbard model on a honeycomb lattice is studied, and a possibility of an antiferromagnetism (AF) at the ground state is examined by Monte Carlo calculations as well as a random phase approximation method. On a single-layer honeycomb lattice, a paramagnetic to AF phase transition occurs at a finite value of the repulsion energy $U_c/t\simeq 3.6$, due to the loss of the density of states at the fermi level. On a layered honeycomb lattice, however, inter-layer hopping term creates a perfect nesting of the fermi surface, and leads the AF with $U_c=0$. From these facts, we discuss that MgB${}_2$ is possibly a nearly-AF metal, where the AF of the 2pz bands is destroyed by carrier doping.

To be published in J. Phys. Soc. Jpn. 70-6. 4 pages with 3 eps figures

References in corpus (4)

• Superconductivity of metallic boron in MgB_2
• Superconductivity of MgB2: Covalent Bonds Driven Metallic
• High-Resolution Photoemission Study of MgB2
• Superconductivity Driven by the Interband Coulomb Interaction and Implications for the Superconducting Mechanism of MgB2

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