Condensed-Matter Physics & Materials Science Seminar

Manganites present a unique opportunity to study a myriad of strongly
correlated electron effects and the interactions between them. However, the
coupling of multiple degrees of freedom - charge, spin,
and lattice - in manganites has mostly been considered at the microscopic
level. On larger length scales, these correlations are affected by strain
and disorder, which can lead to short range order in these phases and affect
the coupling between them. To better understand these effects, we implement
a coherent scattering technique to explore the dynamics of the orbitally
ordered domains near the phase transition in a Ca-doped manganite crystal,
Pr_0.5 Ca_0.5 MnO_3. Our results suggest that this physics is dominated by
the discovery of two competing mechanisms in the nucleation of orbital
domains: quenched domain centers that remain static, and domain boundaries
that exhibit slow, spatiotemporal fluctuations. With heterogeneity being
emphasized over the last decade as a core principle in the array of ordering
mechanisms and colorful properties of doped transition metal oxides, we
demonstrate the importance of an orbital heterogeneity in orbital domains on
the order of a few hundred angstroms, whose length scale and dynamics could
provide the key to the missing ingredient necessary to unlock the secret of
CMR.