Unusual Symmetries in the Kugel-Khomskii Hamiltonian

A. B. Harris, Taner Yildirim, Amnon Aharony, Ora Entin-Wohlman, I. Ya Korenblit

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

The Kugel-Khomskii Hamiltonian for cubic titanates describes spin and orbital superexchange interactions between [Formula presented] ions having threefold degenerate [Formula presented] orbitals. Since orbitals do not couple along “inactive” axes, perpendicular to the orbital planes, the total number of electrons in [Formula presented] orbitals in any such plane and the corresponding total spin are both conserved. A Mermin-Wagner construction shows that there is no long-range spin ordering at nonzero temperatures. Inclusion of spin-orbit coupling allows such ordering, but even then the excitation spectrum is gapless due to a continuous symmetry. Thus, the observed order and gap require more symmetry breaking terms.

Original languageEnglish
JournalPhysical Review Letters
Volume91
Issue number8
DOIs
StatePublished - 21 Aug 2003
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy (all)

Fingerprint

Dive into the research topics of 'Unusual Symmetries in the Kugel-Khomskii Hamiltonian'. Together they form a unique fingerprint.

Cite this