Unconventional Magnetic and Electronic States in Doped Frustrated Magnets
A large class of electronic systems can be described in terms of localized core spins and itinerant fermions. A well-known example is that of manganites where the half-filled t2g levels on Mn give rise to S=3/2 magnetic moments which are well localized, and a partially filled eg band contains the mobile electrons. The superexchange coupling between localized spins competes with the coupling induced via the Kondo-term. The Interplay between these two typically gives rise to very interesting magnetic states, such as the canted state recently observed in manganite heterostructures .
The generic starting point for a theoretical investigation of such systems is the Kondo-lattice-model (KLM). Partly motivated by the observation of anomaleous Hall effect in pyrochlore magnets , we begin by asking a simple question: what happens if the underlying lattice of the KLM is geometrically frustrated? In this seminar I will describe our work that tries to answer the above question. We study the KLM on two frustrated lattices, namely, triangular lattice and checkerboard lattice [3,4].
Our results show that the electronic degrees of freedom can provide a unique way for the magnetic subsystem to release its frustration, leading to unconventional magnetic states and in-turn to novel electronic properties. In case of the checkerboard lattice, a novel connection to graphene and topological insulating states is uncovered.
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