BCS-BEC crossover in a (t<sub>2g</sub>)<sup>4 </sup>excitonic magnet

ORAL

Abstract

In the last few years, the spin-orbit-induced excitonic condensation in multiorbital electronic systems has attracted considerable attention [1-3]. We provide the full λ (spin-orbit coupling) versus Coulomb correlation (U) phase diagrams for both one- and two-dimensional lattices calculated using density matrix renormalization group and Hartree-Fock approximation, respectively [4]. We show that at large and intermediate U regimes, the spin-orbit exciton condensation is possible leading to staggered magnetic order. We show for the first time, the presence of (Bardeen-Cooper-Schrieffer) BCS to BEC crossover in the spin-orbit excitonic condensate. The canonical electron-hole excitations (excitons) transform into local triplon excitations at large U. We also found that at intermediate Hubbard U, increasing λ at fixed U the system transitions from an incommensurate spin-density-wave metal to a BCS excitonic insulator. Further increasing λ, the system eventually crosses over to the BEC limit.

[1] G. Khalliulin, Phys. Rev. Lett. 111, 197201 (2013).
[2] N. Kaushal et al., Phys. Rev. B 96, 155111(2017), Phys. Rev. B 99, 155115 (2019).
[3] C. Svoboda et al., Phys. Rev. B 95, 014409 (2017).
[4] N. Kaushal et al., Phys. Rev. B 101, 245147 (2020).

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Presenters

  • Nitin Kaushal

    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
    • University of Tennessee

Authors

  • Nitin Kaushal

    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
    • University of Tennessee

  • Rahul Soni

    • University of Tennessee
    • Department of Physics and Astronomy, University of Tennessee

  • Alberto Nocera

    • Stewart Blusson Quantum Matter Institute. University of British Columbia.
    • Physics, University of British Columbia
    • University of British Columbia

  • Gonzalo Alvarez

    • Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • Computational Sciences and Engineering Division, Oak Ridge National Laboratory
    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
    • Computational Sciences & Engineering Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
    • Computational Sciences and Engineering Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory

  • Elbio Dagotto

    • University of Tennessee
    • Department of Physics and Astronomy, University of Tennesse at Knoxville
    • Physics, University of Tennessee
    • University of Tennessee and ORNL
    • Department of Physics and Astronomy, University of Tennessee
    • Oak Ridge National Lab