Seminar: “Frustrated Electrons: Competing Interactions and Emergent properties" Prof. Yukitoshi Motome, The University of Tokyo

Seminar Information:

• Date : Fri, Nov 16th 2012
• Time : 10:00 - 11:00  
• Venue : C016, Lab 1, Campus

“Frustrated Electrons: Competing Interactions and Emergent properties”

Prof. Yukitoshi Motome, Department of Applied Physics, The University of Tokyo

    Frustration is a concept for describing the situation in which all preferable conditions cannot be satisfied simultaneously. It is seen in a vastly wide range of phenomena, even in human life and politics. In condensed matter physics, the concept has been explored for the conflict of competing interactions between electrons in solids. A particularly interesting situation is that the frustration emerges even in spatially uniform, regular systems because of the geometry of lattice structures, which is called geometrical frustration. It often gives rise to a macroscopic number of energetically-degenerate states at low temperatures. Such huge degeneracy is a source of fascinating phenomena, such as persistent liquidlike behavior and emergent orderings. The interesting behaviors have been studied for a long time mainly in localized spin systems. Recently, effect of frustration has renewed interest in itinerant electron systems. There, not only spin but also charge degree of freedom of electrons plays a crucial role to modify the structure of the degenerate manifold, leading to a vast and fertile playground for the frustration physics. It is highly nontrivial how the local competition manifests itself in macroscopic properties through the coupling to spatially extended nature of itinerant electrons.

       In this talk, we address the issue of metallic frustration. We review our recent theoretical and numerical results on the emergent properties in spin-charge coupled systems on geometrically-frustrated lattices. The topics will be (i) peculiar phase competition, liquidlike behavior, and anomalous transport properties in a spin-ice type Kondo lattice models on a pyrochlore lattice, and (ii) the quantum topological Hall effect without magnetic ordering in the model on a kagome lattice.