title: Doping-Induced Ferromagnetism and Possible Triplet Pairing in d(4) Mott Insulators.
abstract: We study the effects of electron doping in Mott insulators containing d(4) ions such as Ru(4+), Os(4+), Rh(5+), and Ir(5+) with J=0 singlet ground state. Depending on the strength of the spin-orbit coupling, the undoped systems are either nonmagnetic or host an unusual, excitonic magnetism arising from a condensation of the excited J=1 triplet states of t(2g)(4). We find that the interaction between J excitons and doped carriers strongly supports ferromagnetism, converting both the nonmagnetic and antiferromagnetic phases of the parent insulator into a ferromagnetic metal, and further to a nonmagnetic metal. Close to the ferromagnetic phase, the low-energy spin response is dominated by intense paramagnon excitations that may act as mediators of a triplet pairing.
authors.affiliation: Central European Institute of Technology, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Chaloupka
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
authors.forename: Giniyat
authors.initials: G
authors.lastname: Khaliullin