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@ARTICLE{Zhang:885417,
      author       = {Zhang, Xue-Jing and Koch, Erik and Pavarini, Eva},
      title        = {{O}rigin of orbital ordering in {YT}i{O} 3 and {L}a{T}i{O}
                      3},
      journal      = {Physical review / B},
      volume       = {102},
      number       = {3},
      issn         = {2469-9950},
      address      = {Woodbury, NY},
      reportid     = {FZJ-2020-03814},
      pages        = {035113},
      year         = {2020},
      abstract     = {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.},
      cin          = {JSC / IAS-3 / JARA-HPC},
      ddc          = {530},
      cid          = {I:(DE-Juel1)JSC-20090406 / I:(DE-Juel1)IAS-3-20090406 /
                      $I:(DE-82)080012_20140620$},
      pnm          = {511 - Computational Science and Mathematical Methods
                      (POF3-511) / 144 - Controlling Collective States (POF3-144)
                      / Charge-transfer effects in multi-orbital correlated
                      systems $(jiff46_20191101)$},
      pid          = {G:(DE-HGF)POF3-511 / G:(DE-HGF)POF3-144 /
                      $G:(DE-Juel1)jiff46_20191101$},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000545539900006},
      doi          = {10.1103/PhysRevB.102.035113},
      url          = {https://juser.fz-juelich.de/record/885417},
}