Magnetic properties and Mott transition in the square-lattice Hubbard model with frustration

TL;DR

This study investigates the magnetic behavior and Mott transition in a frustrated square-lattice Hubbard model at zero temperature, revealing a magnetically disordered phase and detailed spectral features across the transition.

Contribution

It provides new insights into the magnetic phases and spectral properties of the frustrated Hubbard model using the variational cluster approximation.

Findings

Disordered magnetic state appears in highly frustrated regions.

Clear spectral gap emerges in the Mott insulator phase.

No incommensurate magnetic states are observed.

Abstract

The magnetic properties and Mott transition of the Hubbard model on the square lattice with frustration are studied at half-filling and zero temperature by the variational cluster approximation. When the on-site repulsion $U$ is large, magnetically disordered state is realized in highly frustrated region between the N\'eel and collinear phases, and no imcommensurate magnetic states are found there. As for the Mott transition, in addition to the Mott gap and double occupancy, which clarify the nature of the transition, the structure of the self-energy in the spectral representation is studied in detail below and above the Mott transition point. The spectral structure of the self-energy is almost featureless in the metallic phase, but clear single dispersion, leading to the Mott gap, appears in the Mott insulator phase.