Hall fluid in the absence of a Magnetic field


Interesting bit of news on the quantum effects in condensed-matter front today:

Writing in the April 24 issue of Nature, the scientists report that they have recorded this exotic behavior of electrons in a bulk crystal of bismuth-antimony without any external magnetic field being present. The work, while significant in a fundamental way, could also lead to advances in new kinds of fast quantum or “spintronic” computing devices, of potential use in future electronic technologies, the authors said.

The quantum Hall effect happens when free electrons in a current carrying material spontaneously get pushed out of the way of the current. The electron’s migrate to the edges of the material (sort of like getting pushed into the eddy pools that are seen at the boundaries of strong water currents). These electrons in toto create their own small electric field, which gives rise to a measurable voltage potential in the material perpendicular to the current flow. This is most easily observed when the migration is “enhanced” by putting the conductor in a transverse magnetic field.

If that’s clear as mud, what’s particularly interesting is that because of the fermi statistics (spin) and the other quantum effects, the migrated electron bundle together in unexpectedly complicated ways, especially so because of the presence of the magnetic field.

But what the paper published this month is pointing out is the experimental verification of something that was suggested theoretically:

“Recently, theorist Charles Kane and his team at the University of Pennsylvania, building upon a model proposed by Duncan Haldane of Princeton, predicted that electrons should be able to form a Hall-like quantum fluid even in the absence of an externally applied magnetic field, in special materials where certain conditions of the electron orbit and the spinning direction are met. The electrons in these special materials are expected to generate their own internal magnetic field when they are traveling near the speed of light and are subject to the laws of relativity. “

Read the full article here.

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