Liquid-like spin dynamics in a hybrid Heisenberg-Ising antiferromagnet

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Abstract
Two-dimensional (2D) materials and their heterostructures enable unconventional electronic properties and functionalities not accessible in their bulk counterparts. This approach is now being extended to magnetic materials to engineer their spin structures and magnetic fields produced by them. However, spin dynamics of 2D magnetic heterostructures remain largely unexplored. Here, we demonstrate that heterointerfacing Heisenberg square-lattice antiferromagnet (AF) Sr2IrO4 with its bilayer variant Ising AF Sr3Ir2O7 in a superlattice leads to liquid-like spin dynamics in the former, characterized by slow recovery of the AF order after its transient suppression by an optical pump, and complete absence of spin waves except in an immediate vicinity of the ordering wavevector. Instead, the spin excitation spectra are dominated by isotropic continua, which in previous works have been interpreted as fractional spin excitations, or spinons, that extends to unprecedentedly low energies. Thus, our results provide a pathway to frustrated magnetism in square lattices by heterointerfacing two distinct types of AFs.
Funding Information
  • Samsung (SSTF-BA2201-04)
  • DOE | LDRD | Argonne National Laboratory (DE-AC02-06CH11357)
  • National Research Foundation of Korea (2018H1A2A1059958)
  • This project is supported by IBS-R014-A2. Experiments at PAL-XFEL and PLS-II were supported by the Ministry of Science and ICT of Korea.

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