
Researchers see signature of “Majorana particles” inside superconducting iron - 4k
http://www.scientificamerican.com/article/majorana-particle-matter-and-antimatter/
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chton
It's an interesting result for solid-state physicists, but the title is very
confusing to the layman. The finding is about quasi particles that have the
same properties as a Majorana fermion (a Majorana bound state), due to how
electrons behave in a superconductor
([https://en.wikipedia.org/wiki/Majorana_fermion#Majorana_boun...](https://en.wikipedia.org/wiki/Majorana_fermion#Majorana_bound_states)).
They did not detect a Majorana fermion itself. This is satisfactorily
explained in the article, but the title is sensationalist.

~~~
jdimov
Trust me, your description is orders of magnitude more confusing to the
layman.

~~~
swombat
Here's the layman's version:

Some particles are actual particles - like photons, electrons, protons, etc.
Think of them as a droplet of water.

Some particles are not really particles, but kind of behave like a particle in
some ways. Think of them as bubbles inside a liquid.

If you ignore the air inside, the bubbles don't really exist - they are just
the absence of some liquid, that happens to look sort of like a particle with
funky properties. Similarly, the particles described in this article don't
really exist - they are "holes" in a lattice of other particles, that can
mathematically be treated as if they were particles, but aren't actually real
in a non-mathematical way.

That said, if Quantum Mechanics has taught us anything, it's that those
"purely mathematical" concepts can have very real impacts on the world, so in
a sense, it is exciting that these "pseudo-particles" have been found to
exist, because the maths might reveal all sorts of funky shit we can do with
them that would be impossible with regular particles, and the maths doesn't
care that they're not regular particles - it works with either kind of
particle.

~~~
tjradcliffe
Good try, and less confusing (or confusing on a much higher level) than some
alternatives, but the use of the word "really" and the implication that
bubbles (and therefore quasi-particles) "don't exist" in this description is
problematic because it is false: bubbles and quasi-particles exist and are as
"really real" as electrons and water-droplets.

Nothing but metaphysical confusion is added by asserting that some things
"really exist" while other perfectly ordinary things--things that can be
created, manipulated, and destroyed--somehow "don't really exist".

A less metaphysically loaded description would be:

The mathematics that Majorana worked out was intended to describe elementary
particles, which as the name suggests can't be divided into their component
parts. It turns out that inside a superconductor, the motion of groups of
electrons, all moving together thanks to the special properties of
superconductors, can be described by the same math. These groups of electrons
can be considered entities in their own right, and are called "quasi-
particles". They are perfectly real: they just aren't elementary.

Furthermore, for quasi-particles the atomic lattice of the superconductor acts
in the same way as empty space does for elementary particles: it gives them a
place to exist and has properties that allow them to move around and interact
with each other. Majorana's equations describes how they do this, so they are
mathematically equivalent to elementary Majorana particles moving around in
empty space.

/End of metaphysical pedantry.

~~~
hahainternet
That isn't pedantry, that's a fantastic description. Thanks for posting it.

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al2o3cr
(facepalm) Another day, another "popularized" article that confuses condensed-
matter quasiparticles with real particles...

~~~
acjohnson55
Honest question:

If what we think of as real particles are really just useful abstractions over
a more complicated reality, but that underlying reality is basically the same
thing mathetmatically that exists in condensed-matter, is there a significant
difference? Where does the analogy break down?

~~~
orbifold
From a theorists perspective there is not much difference, they are both
modeled by Quantum Field Theories. However condensed matter theory deals
mostly with non-relativistic phenomena. The idea of quasiparticles, like the
one they have discovered is also present in particle physics, they are called
"resonances". Depending on the energy scale you can integrate out the higher
energy modes of your theory to get an effective theory, in which those
resonances are now the "fundamental particles", examples include pions, Kaons
etc. This is analogous to how you describe quasi-particles in condensed matter
theory.

In contrast to condensed matter theory which is able to observe electrons on
their own, the fundamental constituents in high energy particle physics have
not all been observed on their own. So called quarks, the building blocks of
protons and neutrons among other things, ordinarily never occur alone, due to
something called confinement. This is analogous to how at low temperature in
super conductors electrons appear as so called cooper pairs coupled by
phonons, here quarks are in a "cosmic superconductor" coupled by gluons. One
of the aims of the LHC experiment is to go to high enough energy to induce a
phase transition to a quark gluon plasma, which would be analogous to the
state electrons are normally in a metal.

So in conclusion, it's not a coincidence that both the renormalization group
by wilson and the idea for the Higgs mechanism, which also has an analogue in
the theory of high temperature superconductivity and was originally proposed
by Anderson in the context of condensed matter theory, were discovered by
theorists working in condensed matter theory.

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kartikkumar
Here's the press announcement in 2012 of the preceeding work done in Delft:
[http://www.tudelft.nl/en/current/latest-
news/article/detail/...](http://www.tudelft.nl/en/current/latest-
news/article/detail/nanowetenschappers-vinden-langgezocht-majorana-deeltje).
And here's a link to the related paper on ArXiV:
[http://arxiv.org/abs/1204.2792](http://arxiv.org/abs/1204.2792).

I know a few of the people working on the experimental setup within the Kavli
Institute. Insanely complex setup! As an aerospace engineer, most of it goes
well over my head, but it's interesting nonetheless!

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lnanek2
> As opposed to particles found in a vacuum, unattached to other matter, these
> Majoranas are what’s called “emergent particles.” They emerge from the
> collective properties of the surrounding matter and could not exist outside
> the superconductor

Sounds a lot like some of the magnetic monopole announcements. It is always
more of a situation than an actual thing.

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calhoun137
This article does demonstrate the principle that virtually every area of
active research in material science, no matter how obscure, will one day have
a Very Important Application in Quantum Computers. _sigh_

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fennecfoxen
Both matter and antimatter? You mean like the photon and, iirc, all the other
neutrally charged elementary particles?

New quasi-particle is Majorana. :b

~~~
chton
There is more to being antimatter than just having the opposite charge. The
spin of the particle also matters. For a particle to be its own antiparticle,
it would have to have spin 1/2\. All elementary fermions have that property,
but not much else.

Of the 2 classes, fermions and bosons, only fermions can be their own
antiparticles. Bosons are defined with having an integer spin, so they can
never have spin 1/2\. Of the fermions, none are known with neutral charge
except for neutrinos, and we're not sure if those are Majorana particles or
not.

Photons, as you mention, are bosons, with spin 1, so they can't be their own
antiparticle.

~~~
mchouza
Photons are generally considered to be their own antiparticles:
[http://van.physics.illinois.edu/qa/listing.php?id=27107](http://van.physics.illinois.edu/qa/listing.php?id=27107)

~~~
chton
Photons are something of a special case because they are massless. Gravitons,
too. As bosons, their interactions are not limited by the Pauli exclusion
principle, so they can not annihilate each other. They interact through
different means (electromagnetic). They're both because they only have the
common properties of particles and their antiparticles.

It's basically like saying "the number 0 is its own negative number". It's
correct according to some definitions, but not useful.

~~~
tagrun
Physicist here. You are confusing things. Having rest mass or Pauli-exclusion
principle has nothing to do with qualification of being an anti-particle.

Z boson, for instance, _does_ have mass and is its own anti-particle.

> It's basically like saying "the number 0 is its own negative number". It's
> correct according to some definitions, but not useful.

Photons have zero _charge_ ; an anti-particle has negative of the particle's
charge (and at the same time, same rest mass and spin).

~~~
chton
Aha, thanks for the correction, I must have picked up some bad info somewhere.
I'll do my research better next time.

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__abc
Is this a marijuana joke?

