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arXiv · 2107.11379

Anomalous magnetic noise in imperfect flat bands in the topological magnet Dy2Ti2O7

Anjana M. Samarakoon·S. A. Grigera·D. Alan Tennant·Alexander Kirste·Bastian Klemke·Peter Strehlow·Michael Meissner·Jonathan N. Hallen·Ludovic Jaubert·Claudio Castelnovo·Roderich Moessner
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Abstract

The spin ice compound Dy_2Ti_2O_7 stands out as the first topological magnet in three dimensions, with its tell-tale emergent fractionalized magnetic monopole excitations. Its real-time dynamical properties have been an enigma from the very beginning. Using ultrasensitive, non-invasive SQUID measurements, we show that Dy_2Ti_2O_7 exhibits a highly anomalous noise spectrum, in three qualitatively different regimes: equilibrium spin ice, a `frozen' regime extending to ultra-low temperatures, as well as a high-temperature `anomalous' paramagnet. We show that in the simplest model of spin ice, the dynamics is not anomalous, and we present several distinct mechanisms which give rise to a coloured noise spectrum. In addition, we identify the structure of the single-ion dynamics as a crucial ingredient for any modelling. Thus, the dynamics of spin ice Dy_2Ti_2O_7 reflects the interplay of local dynamics with emergent topological degrees of freedom and a frustration-generated imperfectly flat energy landscape, and as such should be relevant for a broad class of magnetic materials.

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Anjana M. Samarakoon, S. A. Grigera, D. Alan Tennant, Alexander Kirste, Bastian Klemke, Peter Strehlow, Michael Meissner, Jonathan N. Hallen, Ludovic Jaubert, Claudio Castelnovo, Roderich Moessner. 2021-07-23. Anomalous magnetic noise in imperfect flat bands in the topological magnet Dy2Ti2O7. https://doi.org/10.1073/pnas.2117453119

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