Kavli Affiliate: J. C. Seamus Davis
| First 5 Authors: Jahnatta Dasini, Chaia Carroll, Chun-Chih Hsu, Hiroto Takahashi, Jack Murphy
| Summary:
Dynamical heterogeneity in which transitory local fluctuations occur in the
conformation and dynamics of constituent particles, is essential for evolution
of supercooled liquids into the glass state. Yet its microscopic spatiotemporal
phenomenology has remained unobservable in virtually all supercooled glass
forming liquids. Recent theoretical advances predict that corresponding
dynamical heterogeneity could also occur in supercooled magnetic monopole
fluids. Motivated thus, we searched for dynamical heterogeneity when entering
the supercooled monopole fluid of Dy2Ti2O7. By measuring microsecond-resolved
spontaneous magnetization noise M(t,T) at temperatures between 15 mK<T<2500 mK
we discover a sharp bifurcation in monopole noise characteristics beginning
below T$approx 1500$ mK, with the appearance of powerful monopole current
bursts. This unique new form of dynamical heterogeneity first emerges upon
entering the supercooled monopole fluid regime, reaches maximum intensity near
T$approx 500$ mK and then terminates along with coincident loss of ergodicity
near T$lesssim 250$ mK. Surprisingly, however, low intensity monopole noise
representing activity at approximately 2% of the Dy sites persists below
T$lesssim 250$ mK, implying a population of dynamical monopoles trapped within
the spin-ice ground state as T$rightarrow 0$. This overall phenomenology
significantly expands our knowledge of both supercooled monopole fluids and of
the ground state of spin-ice. More generally, we demonstrate how comprehensive
direct detection of the time sequence, magnitude and statistics of dynamical
heterogeneity can greatly accelerate fundamental vitrification studies.
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