Ivana Petković

Yale University
Cantilever torque magnetometry for the study of topological materials

I will present a proposal to study the magnetic properties of topological materials. The goal of this work will be to directly measure the spin and orbital magnetism in these systems using the high sensitivity and low invasiveness of cantilever torque magnetometry. 

The concept of topological order was introduced in recent years, which provides a unified description of the recently discovered spin-orbit topological insulators in HgTe quantum wells, the quantum spin Hall state in graphene, and the apparently familiar integer and fractional Quantum Hall states. One specific insight provided by this development is that monolayer graphene with the Fermi energy at the zero Landau level and subject to a strong in-plane magnetic field transitions from a canted antiferromagnetic state into a ferromagnetic state followed by the appearance of chiral counterpropagating spin-polarized edge states. However, to date the magnetic order has been inferred indirectly from the transport measurements which reveal these edge states. 

The first goal of my research program will be to study this transition and the resulting magnetic order using magnetization measurements of an electrically isolated sample. Subsequently, this approach will be extended to study fractional quantum Hall states, in which the magnetic nature of the ground states have mostly been inferred from transport and charge compressibility measurements, and magnetic measurements are lacking (similar to graphene). 

As background to these goals, I will also describe the basic features of cantilever torque magnetometry and give an example of how we used it to study mesoscopic superconductivity in isolated metal rings. 

Institut Quantique
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