Tuesday, February 28, 2012

Majorana Fermion detected?

While all eyes are on the LHC to discover new, interesting particles species, condensed matter physicists have been working hard in attempts to detect Majorana fermions and Magnetic Monopoles in solids.  In today's talk at the American Physical Society’s March meeting in Boston, Massachusetts, Leo Kouwenhoven presented findings that Majorana fermions have been detected in an indium antimonide nanowire apparatus.  Indium antimonide nanowires are connected to a circuit with a gold contact at one end and a slice of superconductor at the other, and then exposed to a moderately strong magnetic field. Measurements of the electrical conductance of the nanowires showed a peak at zero voltage that is consistent with the formation of a pair of Majorana particles, one at either end of the region of the nanowire in contact with the superconductor. As a sanity check, the group varied the orientation of the magnetic field and checked that the peak came and went as would be expected for Majorana fermions.

Although other groups have previously reported circumstantial evidence for the appearance of Majorana fermions in solid materials, Jay Sau, a physicist at Harvard University in Cambridge, Massachusetts, who attended Kouwenhoven’s talk, says that this is a direct measurement. “I think this is the most promising-looking experiment yet,” he says. “It would be hard to argue that it’s not Majorana fermions.”

Multiple schemes have been proposed in which Majorana fermions act as the 'bits' in quantum computers, although Sau cautions that it’s not yet clear whether those created by Kouwenhoven will be long-lived enough to be used in that way. 

- Read more at Nature


matpitka@luukku.com said...

I find it a little bit irritating that condensed matter physicists do not bother to tell what they really mean with Majorana property. Now it actually means that electron is effectively its own antiparticle so that electron pair can effectively annihilate. Electrons form a spin 1 Cooper pair "disappearing" into condensate defining the ground state.

I was few years ago frustrated by an analogous completely misleading statement that electrons are massless in graphene and have maximal velocity much below light velocity. If I remember correctly they also decided to refer with spin 1/2 doublet to a pair of two wave functions having nothing do with spin!

As a rule, popularizers forget to ask what these buzz worlds mean and it remains reader's task to distill out all the hype.

kneemo said...

Hi Matti

The experiment is based on papers, such as that by Kitaev (Unpaired Majorana fermions in quantum wires), where Majorana operators are constructed on the boundary of the one-dimensional Fermi systems.