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Majorana fermion detected in a quantum layer cake

Topological insulator plus superconductor yields new evidence for unusual quasiparticle

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3:58pm, July 20, 2017
Majorana fermions in a topological insulator

MAJORANAS IN MOTION  Majorana fermions (blue, red, and purple lines) travel through a topological insulator (horizontal bar) with a superconductor layered on top in this illustration of new experiments to detect the fermions. Green lines indicate electrons travelling on the edges of the topological insulator.

A particle that is its own antiparticle seems to have left its calling card within a solid material.

To observe the signature of that particle, a Majorana fermion, scientists coupled a thin film of a topological insulator — which conducts electricity on its edges but is insulating within — with a layer of a superconductor, in which electrons can flow without resistance. In this layer cake of materials, the researchers report in the July 21 Science, electrical conductivity varied in discrete jumps of the size expected for Majorana fermions. “The experiment came out exactly in the way we predicted,” says theoretical physicist Shoucheng Zhang of Stanford University.

Italian theoretical physicist Ettore Majorana originally proposed in 1937 that these fermions could be a new type of fundamental particle. Instead of having oppositely charged antiparticles, the

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