US-AUST TRANSPACIFIC COLLOQUIUM. Domain and skyrmion bound states on the surface of magnetic topological insulators

Associate Professor, Tami Pereg-Barnea, Department of Physics, McGill University

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A 3D topological insulator (TI) hosts an odd number of Dirac cones as its 2D surface states spectrum. The states are exponentially localized to the surface and their (pseudo)spin is locked to the surface momentum direction due to spin-orbit interaction. If the TI is also magnetic there are fixed magnetic moments on the surface, co-existing with the itinerant Dirac electrons. The magnetic moments interact with each other both directly (exchange) and indirectly (RKKY) and may form a ferromagnetic state. The magnetic state couples to the Dirac electrons and serves as a Dirac mass which, when uniform, opens a gap in the spectrum. When the ordering of the magnetic moments is modified by excitation such as skyrmions and domain walls, the Dirac electrons see a landscape of spatially dependent mass. This leads to localized low energy states around domain walls and skyrmions.
In this talk we will see how the bound states can be detected by a surface conductivity measurement; how the skyrmion-skyrmion interaction is altered due to the presence of Dirac electrons and encounter emergent topological bands in the presence of a skyrmion solid.  *No prior knowledge of the subject is assumed.

Assoc. Prof. Pereg-Barnea’s group works in the field of condensed matter theory. They are interested in systems with unusual properties often related to topological order or strong interactions.
Specifically they study:

• Topological insulators
• Topological superconductors, Majorana fermions
• Floquet topological systems
• Weyl semimetals
• Graphene
• High Tc superconductivity
• Unconventional superconductors (iron-pnictides, cobaltates)

This talk is part of an ongoing series of talks by US and Australian researchers presenting novel developments in condensed matter and cold atomic physics, enriching connections between the two physics communities. Co-presented by FLEET, Monash School of Physics and Astronomy, and the Joint Quantum Institute.

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