Topological insulators and metal-insulator transition in the pyrochlore iridates

By Bohm-Jung Yang, Yong Baek Kim. 2010

145 citations recorded by the source corpus.

The possible existence of topological insulators in cubic pyrochlore iridates ${A}_{2}{\text{Ir}}_{2}{\text{O}}_{7}$ ($A=\text{Y}$ or rare-earth elements) is investigated by taking into account the strong spin-orbit coupling and trigonal crystal-field effect. It is found that the trigonal crystal-field effect, which is always present in real systems, may destabilize the topological insulator proposed for the ideal cubic crystal field, leading to a metallic ground state. Thus the trigonal crystal field is an important control parameter for the metal-insulator changeover. We propose that this could be one of the reasons why distinct low-temperature ground states may arise for the pyrochlore iridates with different $A$-site ions. On the other hand, examining the electron-lattice coupling, we find that softening of the $\mathbf{q}=0$ modes corresponding to trigonal or tetragonal distortions of the Ir pyrochlore lattice leads to the resurrection of the strong topological insulator. Thus, in principle, a finite-temperature transition to a low-temperature topological insulator can occur via structural changes. We also suggest that the application of the external pressure along [111] or its equivalent directions would be the most efficient way of generating strong topological insulators in pyrochlore iridates.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/0b6709d24ec9c5c47b8f6f4ea3dae28d8878d3f2

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In Atomic and Molecular Physics, and Optics

In Condensed Matter Physics

In Materials Chemistry

Citations in the corpus

Topological insulators and superconductors (2010, background): “The QSH effect has been proposed in Na2IrO3 (Shitadeet al., 2009), and topological Mott insulator phases have been proposed in Ir-based pyrochlore oxides Ln2Ir2O7 with Ln = Nd, Pr (Guo and Franz, 2009; Pesin and Balents, 2010; Wanet al., 2010; Yang and Kim, 2010).”