Paramekanti, Arun

Date: Wednesday, June 3, 2015
Time: 11:00
Place: ETH Zurich, Hönggerberg, HIT E 41.1
Host: Sebastian Huber

Unconventional magnetic exchange interactions - from cold atoms to spin-orbit coupled solids

Arun Paramekanti
University of Toronto, Canada

Historically, the Ising and Heisenberg models of magnetism have been important in our understanding of cooperative phenomena in solids. Recent experimental progress in solids and cold atomic gases has enabled the realization of new topological phases driven by spin-orbit coupling or orbital magnetic fields. Can correlated Mott insulators in such systems host unusual magnetic exchange couplings? What is the fingerprint of such unconventional exchange interactions? In this talk, we will explore this issue in the context of the topological Haldane model  of spin-1/2 fermions, where Hubbard repulsion leads to chiral 3-spin exchange interactions and drives noncoplanar tetrahedral magnetic ordering. We will also discuss an example of a geometrically frustrated fcc magnet having iridium ions with strong spin-orbit interactions, where neutron scattering experiments provide evidence for dominant directional couplings due to entanglement of space and spin degrees of freedom.