title: Phase-sensitive observation of a spin-orbital Mott state in Sr2IrO4.
abstract: Measurement of the quantum-mechanical phase in quantum matter provides the most direct manifestation of the underlying abstract physics. We used resonant x-ray scattering to probe the relative phases of constituent atomic orbitals in an electronic wave function, which uncovers the unconventional Mott insulating state induced by relativistic spin-orbit coupling in the layered 5d transition metal oxide Sr2IrO4. A selection rule based on intra-atomic interference effects establishes a complex spin-orbital state represented by an effective total angular momentum = 1/2 quantum number, the phase of which can lead to a quantum topological state of matter.
authors.affiliation: Department of Advanced Materials, University of Tokyo, Kashiwa 277-8561, Japan. bjkim6@gmail.com
authors.forename: B J
authors.initials: BJ
authors.lastname: Kim
authors.forename: H
authors.initials: H
authors.lastname: Ohsumi
authors.forename: T
authors.initials: T
authors.lastname: Komesu
authors.forename: S
authors.initials: S
authors.lastname: Sakai
authors.forename: T
authors.initials: T
authors.lastname: Morita
authors.forename: H
authors.initials: H
authors.lastname: Takagi
authors.forename: T
authors.initials: T
authors.lastname: Arima