Observation of excitons bound by antiferromagnetic correlations

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Abstract
Two-dimensional Mott insulators host antiferromagnetic (AFM) correlations that are predicted to enhance the attractive interaction between empty (holons) and doubly occupied (doublons) sites, creating a novel pathway for exciton formation. However, experimental confirmation of this spin-mediated binding mechanism remains elusive. Leveraging the distinct magnetic critical properties of the Mott antiferromagnets Sr 2 IrO 4 and Sr 3 Ir 2 O 7 , we show using time-resolved THz spectroscopy that excitons exist only at temperatures below where short-range AFM correlation develops. The excitons remain stable up to photodoping densities approaching the predicted excitonic Mott insulator-to-metal transition, revealing a unique robustness against screening. Our results establish the viability of spin-bound excitons and introduce opportunities for excitonic control through magnetic degrees of freedom.
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Funding Information
  • National Science Foundation (DMR-2104833, DMR-1729489)
  • Institute for Quantum Information and Matter, California Institute of Technology (PHY-2317110)
  • University of California, Santa Barbara (DMR-1906325)

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