"Metallic compounds with d- and f-wave electrons in their outer-shell tend to have narrow bandwidths, and their electronic properties can be strongly affected by competing Coulomb interactions. When the Coulomb repulsion is strong enough, the system may become a Mott insulator -- a state in which charge is localized due to the interactions. The study of Mott insulators, and of the mechanisms by which their insulating behavior is destroyed, can give us significant insight regarding nearby metallic and superconducting states.
In the first part of this proposal, I focus on the high-Tc superconducting cuprates. The parent compound in these materials is an antiferromagnetic Mott insulator, which becomes a superconductor upon doping. Doping also leads to spatial inhomogeneity at the nanostructure. I will study the effects of spatial inhomogeneity on the bulk electronic properties, as well its relationship to the superconducting temperature Tc.
In the second part of this proposal, I consider itinerant electron systems on geometrically-frustrated lattices. Geometric frustration helps suppress the formation of magnetic order, and can lead to ``spin-liquid"" states -- Mott insulators with no competing magnetic order. The need to understand spin-liquid states is made more pressing by the advent of newly developed insulators on geometrically-frustrated lattices. I will focus on two related systems:
a) Recent experiments on the hyperkagome compound Na4Ir3O8 demonstrate a pressure-tuned spin-liquid to metal transition in a three-dimensional system. I will study the nature of such a transition and also study the possible existence of a spin liquid phase with spinon pairing in this compound.
b) Motivated by experiments on FeSc2S4, I will study the effects of orbital degeneracy on the Kugel-Khomskii model on the diamond lattice, with the goal to understand the interplay between orbital degeneracy and geometrical frustration in stabilizing spin-liquid states."
Field of science
- /natural sciences/physical sciences/electromagnetism and electronics/electrical conductivity/superconductor
Call for proposal
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