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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