TY  - JOUR
AU  - Zhang, Xue-Jing
AU  - Koch, Erik
AU  - Pavarini, Eva
TI  - Origin of orbital ordering in YTiO 3 and LaTiO 3
JO  - Physical review / B
VL  - 102
IS  - 3
SN  - 2469-9950
CY  - Woodbury, NY
M1  - FZJ-2020-03814
SP  - 035113
PY  - 2020
AB  - The origin of orbital order in correlated transition-metal compounds is strongly debated. For the paradigmatic $e_g$ systems $KCuF_3$ and $LaMnO_3$, it has been shown that the electronic Kugel'-Khomskii mechanism alone is not sufficient to drive the orbital-ordering transition up to the high temperatures at which it is experimentally observed. In the case of $t_{2g}$ compounds, however, the role played by the superexchange interaction remains unclear. Here we investigate this question for two representative systems, the $3dt^1_{2g}$ Mott insulators $LaTiO_3$ and $YTiO_3$. We show that the Kugel'-Khomskii superexchange transition temperature $T_{KK}$ is unexpectedly large, comparable to the value for the $e^3_g$ fluoride $KCuF_3$. By deriving the general form of the orbital superexchange Hamiltonian for the $t^1_{2g}$ configuration, we show that the $GdFeO_3$-type distortion plays a key part in enhancing $T_{KK}$ to about 300 K. Still, orbital ordering above 300 K can be ascribed only to the presence of a static crystal-field splitting.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000545539900006
DO  - DOI:10.1103/PhysRevB.102.035113
UR  - https://juser.fz-juelich.de/record/885417
ER  -