Dichotomous dynamics of magnetic monopole fluids

• 成果类型: Article
• 署名作者: Hsu, Chun Chih; Takahashi, Hiroto; Jerzembeck, Fabian; Dasini, Jahnatta; Carroll, Chaia; Dusad, Ritika; Ward, Jonathan; Dawson, Catherine; Sharma, Sudarshan; Luke, Graeme M.; Blundell, Stephen J.; Castelnovo, Claudio; Hallen, Jonathan N.; Moessner, Roderich; Davis, J. C. Seamus
• 署名单位: University of Oxford; Max Planck Society; University College Cork; McMaster University; University of Cambridge; Max Planck Society; Cornell University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12111
• DOI: 10.1073/pnas.2320384121
• 发表日期: 2024-05-21
• 关键词: spin ice; state

摘要

A recent advance in the study of emergent magnetic monopoles was the discovery that monopole motion is restricted to dynamical fractal trajectories [J. N. Hall & eacute;n et al. , Science 378 , 1218 (2022)], thus explaining the characteristics of magnetic monopole noise spectra [R. Dusad et al., Nature 571 , 234 (2019); A. M. Samarakoon et al. , Proc. Natl. Acad. Sci. U.S.A. 119 , e2117453119 (2022)]. Here, we apply this novel theory to explore the dynamics of field - driven monopole currents, finding them composed of two quite distinct transport processes: initially swift fractal rearrangements of local monopole configurations followed by conventional monopole diffusion. This theory also predicts a characteristic frequency dependence of the dissipative loss angle for AC field-driven currents. To explore these novel perspectives on monopole transport, we introduce simultaneous monopole current control and measurement techniques using SQUID - based monopole current sensors. For the canonical material Dy 2 Ti 2 O 7 , we measure Phi ( t ) , the time dependence of magnetic flux threading the sample when a net monopole current J ( t ) = Phi ( t ) /mu 0 is generated by applying an external magnetic field B 0 ( t ) . These experiments find a sharp dichotomy of monopole currents, separated by their distinct relaxation time constants before and after t - 600 mu s from monopole current initiation. Application of sinusoidal magnetic fields B 0 ( t ) = B cos (co t ) generates oscillating monopole currents whose loss angle 8( f ) exhibits a characteristic transition at frequency f approximate to 1.8 kHz over the same temperature range. Finally, the magnetic noise power is also dichotomic, diminishing sharply after t - 600 li s . This complex phenomenology represents an unprecedented form of dynamical heterogeneity generated by the interplay of fractionalization and local spin configurational symmetry.