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TOPOLOGICAL INSULATORS
Makes your head spin
Phys. Rev. B 92, 201102(R) (2015)
Despite being the first of now many classes of exciting materials whose properties are enriched by the topology of the electronic states, topological insulators still pose a number of challenges. Eric de Vries and colleagues have given us a hint of the sort of problem were facing.
Ideally insulating in the bulk, but with topologically protected conducting surface states, topological insulators have a number of properties that could be exploited in devices. For the spintronics community,the direct coupling between the spin and momentum of the charge carriers in the surface states offers the prospect of injecting and detecting spin currents without the need for ferromagnetic materials.
But de Vries etal. showed that simply measuring the signals due to spins in the surface states of topological insulators is not so easy. With devices capable of measuring the spin signals due to spinmomentum locking in different geometries, they were able to see clear evidence for a spin polarizationof the surface state. The problem is that they can see these signals when spinmomentum locking was clearly not the cause. LF
PRECISION MEASUREMENTS
Martian dune dynamics
Nature Commun. 6, 8796 (2015)
RGB VENTURES / SUPERSTOCK / ALAMY
Planet meets star
Charge conservation
Mon. Not. R.Astron. Soc. (in the press); preprint at http://arxiv.org/abs/1511.02230
Web End =http://arxiv.org/abs/1511.02230 (2015)
Saturns rings are striking but not unique; Jupiter, Uranus and Neptune are similarly girded, as are white dwarf stars. Although we cannot observe the...