Spin-density wave in pnictides: Excitonic instability, dynamics, and transport

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Our overall goal is to better understand the physical properties of the iron pnictides. Several of these compounds have recently been found to become superconducting at remarkably high temperatures. Their magnetic, structural, and transport (conduction) properties in the normal-conducting state are also unconventional. For example, they form antiferromagnetic metals, in contrast to the other important family of high-temperature superconductors, the cuprates, which form antiferromagnetic insulators. The magnetic properties are also crucial for the understanding of superconductivity since magnetic fluctuations are thought to mediate the superconducting interaction. In the first part of the project, we will study the interplay of magnetism and lattice structure, in particular concerning their dynamics. Magnetism and structural properties are known to be coupled but the detailed mechanism is still unclear. In the second part we will consider the unconventional transport of charge and energy. We will calculate the conductivity, the thermopower, and the anomalous Hall effect. In both parts we will address the differences between the various pnictide compounds, in particular the effects of substituting the rare-earth ions.