Hubbard pair cluster in the external fields. Studies of the magnetic properties

TL;DR

This study investigates the magnetic properties of a two-site Hubbard cluster under external electric and magnetic fields using exact diagonalization, revealing field-induced magnetization switching and anomalous temperature behaviors.

Contribution

It provides a detailed analysis of the magnetic behavior of a Hubbard dimer in external fields, including phase diagrams and the effects of temperature, electron concentration, and Coulomb interaction.

Findings

Magnetization and correlation functions exhibit anomalous behavior near critical magnetic fields.

External fields can induce magnetization switching in the Hubbard dimer.

Temperature and Coulomb interaction significantly influence magnetic properties.

Abstract

The magnetic properties of the two-site Hubbard cluster (dimer or pair), embedded in the external electric and magnetic fields and treated as the open system, are studied by means of the exact diagonalization of the Hamiltonian. The formalism of the grand canonical ensemble is adopted. The phase diagrams, on-site magnetization, spin-spin correlations, mean occupation numbers and hopping energy are investigated and illustrated in figures. An influence of temperature, mean electron concentration, Coulomb $U$ parameter and external fields on the quantities of interest is presented and discussed. In particular, the anomalous behaviour of the magnetization and correlation function vs. temperature near the critical magnetic field is found. Also, the effect of magnetization switching by the external fields is demonstrated.