Journal Article

FZJ-2017-05797

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Thermally assisted ordering in Mott insulators

Sims, H. ; Pavarini, E.FZJ* ; Koch, E. (Corresponding author)FZJ*

2017
Inst. Woodbury, NY

This record in other databases:    

Please use a persistent id in citations: http://hdl.handle.net/2128/15298  doi:10.1103/PhysRevB.96.054107

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.

---

Contributing Institute(s):

1. GRS (GRS)
2. Theoretische Nanoelektronik (IAS-3)
3. Jülich Supercomputing Center (JSC)
4. JARA - HPC (JARA-HPC)

Research Program(s):

1. 511 - Computational Science and Mathematical Methods (POF3-511) (POF3-511)
2. 144 - Controlling Collective States (POF3-144) (POF3-144)
3. Multiplet effects in strongly correlated materials (jiff41_20091101) (jiff41_20091101)
4. Order-disorder transitions in strongly correlated systems (jiff46_20101101) (jiff46_20101101)
5. Multiplet effects in strongly correlated materials (jara0050_20130501) (jara0050_20130501)

Appears in the scientific report 2017

---

Database coverage:
; ; ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

---