Magnetic and metal-insulator transitions in coupled spin-fermion systems

R. Mondaini, T. Paiva, and R. T. Scalettar
Phys. Rev. B 90, 144418 – Published 14 October 2014

Abstract

We use quantum Monte Carlo method to determine the magnetic and transport properties of coupled square lattice spin and fermionic planes as a model for a metal-insulator interface. Specifically, layers of Ising spins with an intralayer exchange constant J interact with the electronic spins of several adjoining metallic sheets via a coupling JH. When the chemical potential cuts across the band center, that is, at half-filling, the Néel temperature of antiferromagnetic (J>0) Ising spins is enhanced by the coupling to the metal, while in the ferromagnetic case (J<0), the metallic degrees of freedom reduce the ordering temperature. In the former case, a gap opens in the fermionic spectrum, driving insulating behavior, and the electron spins also order. This induced antiferromagnetism penetrates more weakly as the distance from the interface increases, and also exhibits a nonmonotonic dependence on JH. For doped lattices, an interesting charge disproportionation occurs where electrons move to the interface layer to maintain half-filling there.

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  • Received 14 August 2014

DOI:https://doi.org/10.1103/PhysRevB.90.144418

©2014 American Physical Society

Authors & Affiliations

R. Mondaini1,2, T. Paiva3, and R. T. Scalettar2

  • 1Physics Department, The Pennsylvania State University, 104 Davey Laboratory, University Park, Pennsylvania 16802, USA
  • 2Physics Department, University of California, Davis, California 95616, USA
  • 3Instituto de Física, Universidade Federal do Rio de Janeiro Cx.P. 68.528, 21941-972 Rio de Janeiro RJ, Brazil

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Vol. 90, Iss. 14 — 1 October 2014

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