Surface d-orbital order in an intermetallic compound

Le résumé fourni par la source

Orbital order describes a quantum state where occupied orbitals line up in a periodic pattern. Although orbital physics plays a fundamental and universal role in strongly correlated electron systems, the existence and particularly the band-structure fingerprint of orbital order remain a long-standing mystery. Here we report the discovery of rare earth 5d-orbital order developed by the surface states of the intermetallic compound Tb2CoAl4Ge2. Angle-resolved photoemission spectroscopy reveals characteristic nematic features such as Fermi surface deformation and band splitting. These experimental observations can be described by a ferro-orbital order term in the mean-field Hamiltonian. The structural and magnetic origin of such order is excluded by systematic high-resolution neutron powder diffraction and scanning tunnelling microscopy measurements. Our results provide strong evidence for a pure surface orbital order scenario avoiding complications from structural distortion as in colossal magnetoresistance manganites, magnetic order as in iron-based superconductors and charge transfer p-orbital order in cuprates. Whether orbital order can exist with a clear band-structure fingerprint in correlated materials has remained unresolved. Now an orbital order from rare earth 5d electrons without structural or magnetic order is seen in an intermetallic compound.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.