From multiferroics to cosmology: Scaling behaviour and beyond in the hexagonal manganites (And how electronic structure theory can help)
by
Prof.Nicola Spaldin(ETH Zurich)
→
Europe/Stockholm
122:026
122:026
Description
A key open question in cosmology is whether the vacuum contains
topological defects such as cosmic strings, believed to have formed as a
result of symmetry-lowering phase transitions in the early universe. An
inexpensive, laboratory-based route to shedding light on the answer is
to test the predicted scaling laws for topological defect formation (the
so-called Kibble-Zurek mechanism) in condensed matter systems. Here we
show that the multiferroic hexagonal manganite oxides -- with their
coexisting magnetic, ferroelectric and antiphase orderings -- have an
appropriate symmetry-lowering phase transition for testing the
Kibble-Zurek scenario. We present an analysis of the Kibble-Zurek theory
of topological defect formation applied to the hexagonal magnanites,
show that the recently observed domain vortex cores are formally
topologically protected, and that recent literature data are
quantitatively consistent with our predictions from first-principles
electronic structure theory. Finally, we explore experimentally for the
first time to our knowledge the cross-over out of the Kibble-Zurek
regime and find a surprising "anti-Kibble-Zurek" behavior.
