Yong Baek Kim

Correlated Quantum Phenomena in the Strong Spin-Orbit Regime

We discuss phenomena arising from the combined influence of electron correlation and spin-orbit coupling (SOC), with an emphasis on emergent quantum phases and transitions in heavy transition metal compounds with 4d and 5d elements. A common theme is the influence of spin-orbital entanglement produced by SOC, which influences the electronic and magnetic structure. In the weak-to-intermediate correlation regime, we show how nontrivial band-like topology leads to a plethora of phases related to topological insulators (TIs). We expound these ideas using the example of pyrochlore iridates, showing how many novel phases, such as the Weyl semimetal, axion insulator, topological Mott insulator, and TIs, may arise in this context. In the strong correlation regime, we argue that spin-orbital entanglement fully or partially removes orbital degeneracy, reducing or avoiding the normally ubiquitous Jahn-Teller effect. As we illustrate for the honeycomb-lattice iridates and double perovskites, this leads to enhanced qu...

BERRY PHASE THEORY OF THE ANOMALOUS HALL EFFECT : APPLICATION TO COLOSSAL MAGNETORESISTANCE MANGANITES

We show that the anomalous Hall effect (AHE) observed in colossal magnetoresistance manganites is a manifestation of Berry phase effects caused by carrier hopping in a nontrivial spin background. We determine the magnitude and temperature dependence of the Berry phase contribution to the AHE, finding that it increases rapidly in magnitude as the temperature is raised from zero through the magnetic transition temperature Tc, peaks at a temperature Tmax . Tc, and decays as a power of T , in agreement with experimental data. We suggest that our theory may be relevant to the anomalous Hall effect in conventional ferromagnets as well.

Topological insulators and metal-insulator transition in the pyrochlore iridates

The possible existence of topological insulators in cubic pyrochlore iridates

Topological and magnetic phases of interacting electrons in the pyrochlore iridates

{A}_{2}{\text{Ir}}_{2}{\text{O}}_{7}

Algebraic charge liquids

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Non-Fermi liquid and topological states with strong spin-orbit coupling

A=\text{Y}

Landau level quantization and almost flat modes in three-dimensional semimetals with nodal ring spectra

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

Effect of Structure on the Superconducting Properties of Eutectic Alloys

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Odd-parity triplet superconducting phase in multiorbital materials with a strong spin-orbit coupling: application to doped Sr₂IrO₄.

-site ions. On the other hand, examining the electron-lattice coupling, we find that softening of the

Nonequilibrium quantum criticality in open electronic systems.

\mathbf{q}=0