Reduced density-matrix functionals applied to the Hubbard dimer

Ebad Kamil, Robert Schade, Thomas Pruschke, and Peter E. Blöchl
Phys. Rev. B 93, 085141 – Published 29 February 2016

Abstract

Common density-matrix functionals, the Müller and the power functional, have been benchmarked for the half-filled Hubbard dimer, which allows us to model the bond dissociation problem and the transition from the weakly to the strongly correlated limit. Unbiased numerical calculations are combined with analytical results. Despite the well known successes of the Müller functional, the ground state is degenerate with a one-dimensional manifold of ferromagnetic solutions. The resulting infinite magnetic susceptibility indicates another qualitative flaw of the Müller functional. The derivative discontinuity with respect to particle number is not present indicating an incorrect metal-like behavior. The power functional actually favors the ferromagnetic state for weak interaction. Analogous to the Hartree-Fock approximation, the power functional undergoes a transition beyond a critical interaction strength, in this case, however, to a noncollinear antiferromagnetic state.

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  • Received 7 September 2015
  • Revised 7 December 2015

DOI:https://doi.org/10.1103/PhysRevB.93.085141

©2016 American Physical Society

Authors & Affiliations

Ebad Kamil1, Robert Schade2, Thomas Pruschke1, and Peter E. Blöchl2,3

  • 1Institute for Theoretical Physics, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
  • 2Institute for Theoretical Physics, Clausthal University of Technology, Leibnizstr. 10, 38678 Clausthal-Zellerfeld, Germany
  • 3Institute for Materials Physics, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

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Issue

Vol. 93, Iss. 8 — 15 February 2016

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