Giant Spin Gap and Magnon Localization in the Disordered Heisenberg Antiferromagnet Sr2Ir1-xRuxO4
ORAL
Abstract
We study the evolution of magnetic excitations in the disordered two-dimensional antiferromagnet Sr\textunderscore 2Ir\textunderscore 1-xRu\textunderscore xO\textunderscore 4. A gigantic magnetic gap greater than 40 meV opens at x $=$ 0.27 and increases with Ru concentration, from 40 meV to \textgreater 150 meV, rendering the dispersive magnetic excitations in Sr2IrO4 almost momentum independent. Up to a Ru concentration of x $=$ 0.77, both experiments and first-principles calculations show the Ir J\textunderscore eff $=$ 1/2 state remains intact. The magnetic gap arises from the local interaction anisotropy in the proximity of the Ru disorder. Under the coherent potential approximation, we reproduce the experimental magnetic excitations using the disordered Heisenberg antiferromagnetic model with suppressed next-nearest neighbor ferromagnetic coupling. Ref: Y. Cao et al., arXiv:1608.04640 (2016).
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