Block spin magnetism and metal-insulator transition in a two-dimensional Hubbard model with perfect vacancy superstructure

Abstract

We study the phase diagram of a square lattice Hubbard model with a perfect vacancy superstructure. The model can be also defined on a new bipartite lattice with each building blocks consisting of a minimal square. The non-interacting model is exactly solved and a mid-band gap opens at the Fermi energy in the weak inter-block hopping regime. Increasing the Coulomb interaction will develop the Néel antiferromagnetic order with varying block spin moments. The metal-insulator transition with $U_{\mathrm{MI}}$ smaller than the one without vacancies occurs above the magnetic instability $U_{\mathrm{M}}$. The emergent intermediate magnetic metal phase develops substantially in the moderate inter-block hopping regime. Drastic increases in the ordered moment and gap magnitude on the verge of non-interacting band insulator signal a possible distinction between the magnetic semi-conductor and the Mott-insulator. The implications of these results for the recent discovered (A,Tl)${}_y$Fe${}_{2-x}$Se${}_2$ compounds are discussed.

4+ pages, 5 figures, references and note updated based on the published version

References in corpus (6)

• Fe-based high temperature superconductivity with Tc=31K bordering an insulating antiferromagnet in (Tl,K)FexSe2 Crystals
• Superconductivity at 32K and anisotropy in Tl0.58Rb0.42Fe1.72Se2 crystals
• Electronic structures and magnetic orders of Fe-vacancies ordered ternary iron selenides TlFe${}_{1.5}$Se${}_2$ and AFe${}_{1.5}$Se${}_2$ (A=K, Rb, or Cs)
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• Room temperature antiferromagnetic order in superconducting X_yFe_{2-x}Se_ 2, (X= Rb, K): a powder neutron diffraction study
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Cited by in corpus (5)

• The Unexpected Properties of Alkali Metal Iron Selenide Superconductors
• Vacancy Driven Orbital and Magnetic Order in (K,Tl,Cs)${}_y$Fe${}_{2-x}$Se${}_2$
• Dynamic approach to finite-temperature magnetic phase transitions in the extended J1- J2 model with vacancy order
• Spin triplet pairing by suppressing altermagnetism
• Quasiparticle Scattering Interference in (K,Tl)FexSe2 Superconductors