Dichotomous Dynamics of Magnetic Monopole Fluids
Journal Articles
Overview
Research
Identity
Additional Document Info
View All
Overview
abstract
A recent advance in the study of emergent magnetic monopoles was the discovery that monopole motion is restricted to dynamical fractal trajectories [J. N. Hallén
et al.
,
Science378
, 1218 (2022)], thus explaining the characteristics of magnetic monopole noise spectra [R. Dusad
et al., Nature571
, 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
Φ(t)
, the time dependence of magnetic flux threading the sample when a net monopole current
Jt=Φ˙(t)/μ0
is generated by applying an external magnetic field
B0t.
These experiments find a sharp dichotomy of monopole currents, separated by their distinct relaxation time constants before and after
t
~
600μs
from monopole current initiation. Application of sinusoidal magnetic fields
B0t=Bcosωt
generates oscillating monopole currents whose loss angle
θf
exhibits a characteristic transition at frequency
f≈1.8kHz
over the same temperature range. Finally, the magnetic noise power is also dichotomic, diminishing sharply after
t
~
600μs
. This complex phenomenology represents an unprecedented form of dynamical heterogeneity generated by the interplay of fractionalization and local spin configurational symmetry.
