Wednesday, September 26, 2012

More Evidence On Majorana Fermions

On the heels of the possible discovery of Majorana fermions earlier this year, along comes more evidence of their discovery, and this time, they came from a Josephson experiment.

Rokhinson observed a variation of the Josephson effect that is a unique signature of Majorana fermions. The effect describes the way an electrical current traveling between two superconductors oscillates at a frequency that depends on the applied voltage. The reverse also is true; an oscillating current generates specific voltage, proportional to the frequency. In the presence of Majorana fermions the frequency-voltage relationship should change by a factor of two in what is called the fractional a.c. Josephson effect, he said.

Rokhinson used a one-dimensional semiconductor coupled to a superconductor to create a hybrid nanowire in which Majorana particles are predicted to form at the ends. When alternating current is applied through a set of two such wires, a specific voltage is generated across the device, which Rokhinson measured. As a magnetic field was applied and varied from weak to strong, the resulting steps in voltage became twice as tall, a signature of the formation of Majorana particles, he said.
There ya go! So far, in the race to detect the existence of the Majorana particles, it is two for condensed matter physics, and zero for high energy physics.


1 comment:

HM said...

I have always disliked the fact that the zero-modes bound to vortices/domain wall/other topological defects, and has non-abelian statistics, are called "Majorana fermions". This lead people to confuse them with Majorana fermions of high energy physics, these two are very different objects. For example in high energy physics Majorana fermions ARE fermions, while in condensed matter physics they are not (this IS the reason why we are so interested in them in the first place). There are of course some work which describe these anyons as true fermions coupled to a BF-theory, and the non-abelian nature pops out after integrating out the BF-gauge fields.

However, I still believe that people stretch the analogy way too far by comparing Majorana fermions of high energy physics, and condensed matter physics. You could also call mesons for "Room Temp. superconductors", then say "1 - 0 to high energy physics since they found a Room Temp. superconductor". Its just a name, it doesn't say the physics is similar at all.