THESIS
2017
xv, 64 pages : illustrations ; 30 cm
Abstract
Geometrical frustration arises when the lattice geometry prevents local interaction
energies from minimizing simultaneously. Whether and how geometrically
frustrated spins or charges in clean crystals exhibit glassy dynamics remain
elusive due to the lack of measurements on microscopic dynamics. Here we
employed buckled monolayer colloidal crystals to mimic frustrated antiferromagnetic
Ising spins on triangular lattices, and measured single-spin dynamics using
video microscopy. Both attractive and repulsive colloidal crystals buckled into
zigzag stripes with glassy dynamics at low effective temperatures in experiment
and simulation. The simple local spin configurations enable uncovering correlations
among structure, dynamics and soft vibrational modes. Machine learning
analysi...[
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Geometrical frustration arises when the lattice geometry prevents local interaction
energies from minimizing simultaneously. Whether and how geometrically
frustrated spins or charges in clean crystals exhibit glassy dynamics remain
elusive due to the lack of measurements on microscopic dynamics. Here we
employed buckled monolayer colloidal crystals to mimic frustrated antiferromagnetic
Ising spins on triangular lattices, and measured single-spin dynamics using
video microscopy. Both attractive and repulsive colloidal crystals buckled into
zigzag stripes with glassy dynamics at low effective temperatures in experiment
and simulation. The simple local spin configurations enable uncovering correlations
among structure, dynamics and soft vibrational modes. Machine learning
analysis further revealed facilitated dynamics to be an important mechanism of
structural relaxation. Moreover, our simulation revealed a similar structure and
dynamics in lattice Coulomb liquids. Hence, spin-lattice coupling and long-range
interaction can similarly lift degeneracy, induce a rugged landscape and thus produce
glassy dynamics. With machine learning methods, we can further resolve
the relation between facilitation and local structural signatures.
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