Synopsis: Weyl Metals as Proxies for Astrophysical Dynamos

Certain topological materials could be used in lab tests of the dynamo effect, thought to generate magnetic fields in stars and planets.

Planets and stars can create magnetic fields that persist for billions of years. These fields, according to dynamo theory, arise from electric currents created by the movements of viscous, electrically conducting fluids in the outer core of the star or planet. This theory, however, cannot fully explain astrophysical observations, so researchers have been testing it in controlled laboratory experiments. Now, Victor Galitski at the University of Maryland, College Park, and colleagues propose that the dynamo effect could be observed in a recently discovered class of topological materials known as Weyl metals—solids in which electronic excitations behave as massless fermions. These materials could provide an experimental platform that is simpler than previous lab setups and could be tuned to mimic astrophysical conditions.

Galitski and colleagues study charge transport in a Weyl metal, showing that it can exhibit effects, such as turbulence, that are encountered in weakly viscous fluids. They find that charge motion in the material is governed by the same equations that underlie dynamo theory: the Navier-Stokes equations for viscous fluids coupled to the Maxwell equations for electromagnetism. The team finds the conditions under which a dynamo effect can arise in a Weyl metal by calculating a crucial figure of merit for dynamos: the magnetic Reynolds number, a parameter that quantifies whether the magnetic field configuration is determined by bulk movement or by diffusion. The result shows that this number can be large enough to generate a dynamo-induced field that could be detected in experiments.

This research is published in Physical Review Letters.

–Matteo Rini

Matteo Rini is the Deputy Editor of Physics.


Features

More Features »

Announcements

More Announcements »

Subject Areas

MagnetismGeophysicsCondensed Matter Physics

Previous Synopsis

Next Synopsis

Nuclear Physics

The Fastest Alpha Emitter

Read More »

Related Articles

Viewpoint: A Quasicrystal for Quantum Simulations
Condensed Matter Physics

Viewpoint: A Quasicrystal for Quantum Simulations

Experimentalists realize a Bose-Einstein condensate on a 2D quasicrystal optical lattice, opening the path for simulations of a variety of quantum many-body phenomena in these fractal structures. Read More »

Synopsis: The Signature of Magnetic Monopoles
Magnetism

Synopsis: The Signature of Magnetic Monopoles

Calcu­lations uncover the neutron-scattering signature of the magnetic monopoles that propagate through quantum spin ices. Read More »

Focus: Muons Reveal Record-Breaking Thunderstorm Voltage
Geophysics

Focus: Muons Reveal Record-Breaking Thunderstorm Voltage

A thunderstorm probed with atmospheric muons had an electric potential exceeding one billion volts, much higher than values measured previously.   Read More »

More Articles