Theoretical Physics

20 April 2016
Time: 12:00 to 13:00
Location: EC Stoner 8.62

Theoretical Physics Seminar: Felix Flicker (UC Berkeley)

EC Stoner 8.62

The Gyrotropic Magnetic Effect

There has been a great deal of interest recently in so-called Weyl 
Semi-Metals. These materials are simple to characterize theoretically, 
but demonstrate a range of topological phenomena while lacking an energy 
gap at the Fermi level. An erroneous example of such a phenomenon is the 
Chiral Magnetic Effect, in which it was believed a static magnetic field 
could drive a dissipationless current in Weyl Semi-Metals lacking 
inversion symmetry. Although now known to be incorrect, the theory lead 
to the understanding of a much more general phenomenon, the Gyrotropic 
Magnetic Effect, which is predicted to appear in a wide range of 
inversion-broken metals. This effect turns out to be the low-frequency 
limit of natural optical activity, where the plane of polarization of 
linearly polarized light is rotated by inversion-broken crystals.

In this talk I will give an overview of the history of these phenomena, 
before outlining two pieces of ongoing work. The first concerns the 
natural optical activity of quartz, which remarkably still contains an 
unresolved mystery despite being observed over 200 years ago. The second 
concerns a proposal to use the gyrotropic magnetic effect as a probe of 
another novel theoretical proposal, a `chiral charge density wave' in 
the transition metal dichalcogenide titanium diselenide.



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