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Abstract: We examine a novel type of disorder in quantum antiferromagnets. Our modelconsists of localized spins with antiferromagnetic exchanges on a bipartitequasiperiodic structure, which is geometrically disordered in such a way thatno frustration is introduced. In the limit of zero disorder, the structure isthe perfect Penrose rhombus tiling. This tiling is progressively disordered byaugmenting the number of random -phason flips- or local tile-reshufflingoperations. The ground state remains N\-eel ordered, and we have studied itsproperties as a function of increasing disorder using linear spin wave theoryand quantum Monte Carlo. We find that the ground state energy decreases,indicating enhanced quantum fluctuations with increasing disorder. The magnonspectrum is progressively smoothed, and the effective spin wave velocity of lowenergy magnons increases with disorder. For large disorder, the ground stateenergy as well as the average staggered magnetization tend towards limitingvalues characteristic of this type of randomized tilings.



Author: Attila Szallas, Anuradha Jagannathan, Stefan Wessel

Source: https://arxiv.org/



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