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Excitonic magnetism at the intersection of spin-orbit coupling and crystal-field splitting

Teresa Feldmaier1, Pascal Strobel1, Michael Schmid1,2, Philipp Hansmann3,4, and Maria Daghofer1,2

  • 1Institute for Functional Matter and Quantum Technologies, University of Stuttgart, 70550 Stuttgart, Germany
  • 2Center for Integrated Quantum Science and Technology, University of Stuttgart, 70550 Stuttgart, Germany
  • 3Max-Planck-Institute for Chemical Physics of Solids, 01187 Dresden, Germany
  • 4Department of Physics, University of Erlangen-Nuremberg, 91058 Erlangen, Germany
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Phys. Rev. Research 2, 033201 – Published 5 August, 2020

DOI: https://doi.org/10.1103/PhysRevResearch.2.033201

Abstract

Excitonic magnetism involving superpositions of singlet and triplet states is expected to arise for two holes in strongly correlated and spin-orbit-coupled t2g orbitals. However, uncontested material examples for its realization are rare. We apply the variational cluster approach to the square lattice to investigate excitonic antiferromagnetism and the impact of a crystal field. We give a phase diagram depending on spin-orbit coupling and crystal field and find excitonic magnetism to survive in the presence of substantial crystal-field-induced orbital order. We address the specific example of Ca2RuO4 using ab initio modeling and conclude it to realize such excitonic magnetism despite its pronounced orbital polarization. We also reproduce magnetic excitations and show the maximum at momentum (0,0) to be related to the excitonic character of the magnetic order.

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Article Text

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Phys. Rev. Research 2, 033201– Published 5 August, 2020
  • Received 11 November 2019
  • Revised 16 June 2020
  • Accepted 17 June 2020
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