Mott physics and band topology in materials with strong spin-orbit interaction

Recent theory and experiment have revealed that strong spin–orbit coupling can have marked qualitative effects on the band structure of weakly interacting solids, leading to a distinct phase of matter, the topological band insulator. We show that spin–orbit interaction also has quantitative and qual...

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Bibliographic Details
Published in:Nature physics 2010-05, Vol.6 (5), p.376-381
Main Authors: Pesin, Dmytro, Balents, Leon
Format: Article
Language:English
Subjects:
Atomic
Band structure of solids
Band theory
Classical and Continuum Physics
Complex Systems
Condensed Matter Physics
Insulators
Iridium
Joining
Mathematical and Computational Physics
Molecular
Optical and Plasma Physics
Orbits
Phase diagrams
Physics
Physics and Astronomy
Pyrochlores
Spin-orbit interactions
Theoretical
Topology
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Summary:Recent theory and experiment have revealed that strong spin–orbit coupling can have marked qualitative effects on the band structure of weakly interacting solids, leading to a distinct phase of matter, the topological band insulator. We show that spin–orbit interaction also has quantitative and qualitative effects on the correlation-driven Mott insulator transition. Taking Ir-based pyrochlores as a specific example, we predict that for weak electron–electron interaction Ir electrons are in metallic and topological band insulator phases at weak and strong spin–orbit interaction, respectively. We show that by increasing the electron–electron interaction strength, the effects of spin–orbit coupling are enhanced. With increasing interactions, the topological band insulator is transformed into a ‘topological Mott insulator’ phase having gapless surface spin-only excitations. The proposed phase diagram also includes a region of gapless Mott insulator with a spinon Fermi surface, and a magnetically ordered state at still larger electron–electron interaction. Mott insulators are driven by strong Coulomb repulsion and topological insulators by strong spin–orbit coupling. Although these effects are normally in competition, in some cases the Coulomb interaction can enhance the effects of spin–orbit coupling. Together these interactions could lead to gapless spin-only excitations on the surface of a strongly correlated insulator.
ISSN:1745-2473
1745-2481
DOI:10.1038/nphys1606