Phase-sensitive observation of a spin-orbital Mott state in Sr2IrO4.

Kim, B J; Ohsumi, H; Komesu, T; Sakai, S; Morita, T; Takagi, H; Arima, T · Science · 2009

basic_science · Level V

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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.