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@ARTICLE{Sims:836738,
author = {Sims, Hunter and Pavarini, Eva and Koch, Erik},
title = {{T}hermally assisted ordering in {M}ott insulators},
journal = {Physical review / B},
volume = {96},
issn = {0163-1829},
address = {Woodbury, NY},
publisher = {Inst.},
reportid = {FZJ-2017-05797},
pages = {054107},
year = {2017},
abstract = {Landau theory describes phase transitions as the
competition between energy and entropy: The ordered phase
has lower energy, while the disordered phase has larger
entropy. When heating the system, ordering is reduced
entropically until it vanishes at the critical temperature.
This picture implicitly assumes that the energy difference
between the ordered and disordered phases does not change
with temperature. We show that for orbital ordering in the
Mott insulator KCuF3, this assumption fails qualitatively:
entropy plays a negligible role, while thermal expansion
energetically stabilizes the orbitally ordered phase to such
an extent that no phase transition is observed. To
understand this strong dependence on the lattice constant,
we need to take into account the Born-Mayer repulsion
between the ions. It is the latter, and not the Jahn-Teller
elastic energy, which determines the magnitude of the
distortion. This effect will be seen in all materials where
the distortion expected from the Jahn-Teller mechanism is so
large that the ions would touch. Our mechanism explains not
only the absence of a phase transition in KCuF3, but even
suggests the possibility of an inverted transition in
closed-shell systems, where the ordered phase emerges only
at high temperatures.},
cin = {GRS / IAS-3 / JSC / JARA-HPC},
ddc = {530},
cid = {I:(DE-Juel1)GRS-20100316 / I:(DE-Juel1)IAS-3-20090406 /
I:(DE-Juel1)JSC-20090406 / $I:(DE-82)080012_20140620$},
pnm = {511 - Computational Science and Mathematical Methods
(POF3-511) / 144 - Controlling Collective States (POF3-144)
/ Multiplet effects in strongly correlated materials
$(jiff41_20091101)$ / Order-disorder transitions in strongly
correlated systems $(jiff46_20101101)$ / Multiplet effects
in strongly correlated materials $(jara0050_20130501)$},
pid = {G:(DE-HGF)POF3-511 / G:(DE-HGF)POF3-144 /
$G:(DE-Juel1)jiff41_20091101$ /
$G:(DE-Juel1)jiff46_20101101$ /
$G:(DE-Juel1)jara0050_20130501$},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000407096800001},
doi = {10.1103/PhysRevB.96.054107},
url = {https://juser.fz-juelich.de/record/836738},
}