Researchers find possible evidence of Majorana fermions

Apr 13, 2012 by Bob Yirka report
Two Majorana fermions (orange balls) are formed at the end of the nanowire. Electrons enter the nanowire from the Gold contact, and meet the Majorana fermion on the way. If the electron has the wrong energy (red ball), it is reflected back into the contact. If it has the right energy (green balls), it can go through the Majorana fermion via a special interaction. © TU Delft 2012

( -- Researchers working out of Delft University of Technology in the Netherlands have constructed a device that appears to offer some evidence of the existence of Majorana fermions; the elusive particles that are thought to be their own antiparticles. The team, as they describe in their paper published in Science, created a device with a topological superconductor that was also able to measure the relationship between current and voltage at significant points on a nanowire which when in the presence of a magnetic field or electrical current, indicated the existence of Majorana fermions.

Majorana fermions are electrically neutral of matter first theorized by Ettore Majorana in 1937. Unlike other particles such as electrons which correspond with their antimatter counterparts positrons, Majorana fermions have no antimatter mate, they serve as their own , and because of that, researchers believe they might one day be useful in creating quantum computers, because when moved, they are believed to have a property that allows them to remember their former position.

The device is made of an Indium Antemonide nanowire, covered with a Gold contact and partially covered with a Superconducting Niobium contact. The Majorana fermions are created at the end of the Nanowire. © TU Delft 2012

To try to show that Majorana fermions can be observed, the team built a device that employed the use of a topological superconductor, which is a material that has an inner part that has zero while the outer part is a normal conductor. Prior to this experiment, theorists had predicted that such a material would have Majorana fermions in it.

To create a device that would have both the right material and a means of measuring Majorana fermions, the team connected an indium antimonide nanowire in between an electrode made of gold and the end of a superconducting material. They then placed the result onto a which had been preprinted with to allow for reading the electronic properties of the nanowire. With the stage set, the team then cooled the device to just fractions of degrees above absolute zero and then introduced a magnetic field at one point and additional current at another. In both instances, the researchers found that at two points along the wire, their device registered a strong response at just the places where Majorana fermions were predicted to occur. The responses in effect showed that the particles didn’t move when in the presence of a magnetic field or an electric current, because they are electrically neutral.

This video is not supported by your browser at this time.
Conceptual explanation of the Majorana experiment. Video: TU Delft

In contrast, when any of the elements in the device were changed, the responses did not occur, showing that the device they had built did indeed match the theory behind it.

This experiment doesn’t exactly show the existence of Majorana fermions, as the researchers readily acknowledge, but it does offer strong evidence that not only do they exist, but that their properties can be demonstrated, which is a major step forward in the study of particle physics.

Explore further: Using antineutrinos to monitor nuclear reactors

More information: Signatures of Majorana Fermions in Hybrid Superconductor-Semiconductor Nanowire Devices, Science, DOI: 10.1126/science.1222360

Majorana fermions are particles identical to their own antiparticles. They have been theoretically predicted to exist in topological superconductors. We report electrical measurements on InSb nanowires contacted with one normal (Au) and one superconducting electrode (NbTiN). Gate voltages vary electron density and define a tunnel barrier between normal and superconducting contacts. In the presence of magnetic fields of order 100 mT, we observe bound, mid-gap states at zero bias voltage. These bound states remain fixed to zero bias even when magnetic fields and gate voltages are changed over considerable ranges. Our observations support the hypothesis of Majorana fermions in nanowires coupled to superconductors.

Related Stories

Third research team close to creating Majorana fermion

Mar 16, 2012

( -- Recently there has been a virtual explosion of research efforts aimed at creating the elusive Majorana fermion with different groups claiming to be near to creating them. First there was news that a team ...

Physicists move one step closer to quantum computer

Oct 04, 2011

Rice University physicists have created a tiny "electron superhighway" that could one day be useful for building a quantum computer, a new type of computer that will use quantum particles in place of the digital ...

Exotic quantum states: A new research approach

Oct 03, 2011

( -- Theoretical physicists of the University of Innsbruck have formulated a new concept to engineer exotic, so-called topological states of matter in quantum mechanical many-body systems. They ...

Recommended for you

Using antineutrinos to monitor nuclear reactors

43 minutes ago

When monitoring nuclear reactors, the International Atomic Energy Agency has to rely on input given by the operators. In the future, antineutrino detectors may provide an additional option for monitoring. ...

Imaging turns a corner

4 hours ago

( —Scientists have developed a new microscope which enables a dramatically improved view of biological cells.

Mapping the road to quantum gravity

18 hours ago

The road uniting quantum field theory and general relativity – the two great theories of modern physics – has been impassable for 80 years. Could a tool from condensed matter physics finally help map ...

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

4.9 / 5 (12) Apr 13, 2012
Fermion my wayward son,
They'll find no charge when you are spun!
But if you meet another one,
Annihila - a - tion!
1 / 5 (1) Apr 13, 2012
Fermion my wayward son,
They'll find no charge when you are spun!
But if you meet another one,
Annihila - a - tion!

5 / 5 (3) Apr 14, 2012
This research was financed by the FOM Foundation and Microsoft. Microsoft approached Leo Kouwenhoven to help them lead a special FOM programme in search of Majorana fermions, resulting in a successful outcome.
not rated yet Apr 16, 2012
I cannot find a any decent description of a Majorana fermion. For instance, is it an elementary particle or a composite particle? Mass, charge, spin?

More news stories

Using antineutrinos to monitor nuclear reactors

When monitoring nuclear reactors, the International Atomic Energy Agency has to rely on input given by the operators. In the future, antineutrino detectors may provide an additional option for monitoring. ...

When things get glassy, molecules go fractal

Colorful church windows, beads on a necklace and many of our favorite plastics share something in common—they all belong to a state of matter known as glasses. School children learn the difference between ...

Bake your own droplet lens

A droplet of clear liquid can bend light, acting as a lens. Now, by exploiting this well-known phenomenon, researchers have developed a new process to create inexpensive high quality lenses that will cost ...

How do liquid foams block sound?

Liquid foams have a remarkable property: they completely block the transmission of sound over a wide range of frequencies. CNRS physicists working in collaboration with teams from Paris Diderot and Rennes ...

New breast cancer imaging method promising

The new PAMmography method for imaging breast cancer developed by the University of Twente's MIRA research institute and the Medisch Spectrum Twente hospital appears to be a promising new method that could ...

Research proves nanobubbles are superstable

The intense research interest in surface nanobubbles arises from their potential applications in microfluidics and the scientific challenge for controlling their fundamental physical properties. One of the ...