
Caltech announces discovery in fundamental physics - jonbaer
http://phys.org/news/2015-08-caltech-discovery-fundamental-physics.html
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InclinedPlane
Hmmm, interesting. If I understand correctly this is a breakthrough in our
understanding of the underlying physics related to superconductivity. Which
could potentially lead not just to an improved understanding of
superconductivity and toward new kinds of superconductors but also to new
electronic phenomena in metals which might possibly be equally as interesting.
This is a significant breakthrough in condensed matter physics, which may end
up being one brick of a foundation of theoretical models which form the basis
of a vastly superior understanding of matter compared to what we have today.
Which might potentially enable uses that we cannot even envision today. Pretty
exciting stuff.

~~~
selimthegrim
Well this is debatable. These anomalies figure into the so-called nodal gap in
the antiferromagnetic, not the superconducting phase, of certain high
temperature superconductors. There is hope that this might spread light on the
nature of superconductivity.

~~~
InclinedPlane
Right. There's a lot of maybes and potentially with this research. It's
something new and interesting but how much it will allow us to unlock some of
the secrets of condensed matter physics that have so far eluded us remains to
be proven.

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pmalynin
Obligatory [http://sci-hub.org/10.1038/nphys3416](http://sci-
hub.org/10.1038/nphys3416)

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cgs1019
Looks like Nature makes the whole paper readable online:
[http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys...](http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3416.html)

~~~
stephengillie
Not to me it doesn't. I see this near the bottom of the page:

    
    
      READ THE FULL ARTICLE
    
      Subscribe to      Purchase article
      Nature Physics    full text and PDF:
      for full access:  $32
      $175              [Buy Now]
      [Subscribe]
    

Edit: Thanks Mr. M.

~~~
jacquesm
[http://iopscience.iop.org/1742-6596/626/1/012012/pdf/1742-65...](http://iopscience.iop.org/1742-6596/626/1/012012/pdf/1742-6596_626_1_012012.pdf)

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cowsandmilk
this is not the article.

~~~
jacquesm
Ai sorry, I thought it was the pre-press version of the paper.

See:

[https://news.ycombinator.com/item?id=10037257](https://news.ycombinator.com/item?id=10037257)

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chockablock
Here is the free full-text (provided by Nature as an in-browser read-only
version): [http://rdcu.be/dCSH](http://rdcu.be/dCSH)

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eranation
Would anyone ELI5 please?

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dghughes
Got a non-spammy link?

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skew
[http://www.caltech.edu/news/caltech-announces-discovery-
fund...](http://www.caltech.edu/news/caltech-announces-discovery-fundamental-
physics-47485)

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astroteller
Free supplementary materials PDF here:
[http://authors.library.caltech.edu/58610/3/nphys3416-s1.pdf](http://authors.library.caltech.edu/58610/3/nphys3416-s1.pdf)

Edit: thanks for the downvotes!

~~~
andy_ppp
I really don't think down voting is very helpful for the community unless
people are being racist/sexist/obvious troll. Better people comment on why
they disagree, clarifying ideas rather than a no response and arbitrary
unlike.

~~~
duaneb
Yea, I don't downvote comments unless they are straight-up counterproductive
to conversation. The original comment is very useful.

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david-given
tl;dr abstract of the paper:

\---snip---

Abstract. Instabilities of equilibrium quantum mechanics are common and well-
understood. They are manifested for example in phase transitions, where a
quantum system becomes so sensitive to perturbations that a symmetry can be
spontaneously broken. Here, we consider the possibility that the time
evolution governing quantum dynamics may be similarly subject to an
instability, at which its unitarity spontaneously breaks down owing to an
extreme sensitivity towards perturbations. We find that indeed such an
instability exists, and we explore its immediate consequences. Interpretations
of the results both in terms of extreme sensitivity to the influence of
environmental degrees of freedom, and in terms of a possible fundamental
violation of unitarity are discussed.

\---snip---

Is this suggesting that quantum superpositions have a tendency to
spontaneously collapse, or am I misreading it?

~~~
selimthegrim
Uh, this isn't the abstract of that nature paper at all

~~~
david-given
You're quite right. It's not. This is the correct abstract:

\---snip---

Charge ordering in metals is a fundamental instability of the electron sea,
occurring in a host of materials and often linked to other collective ground
states such as superconductivity. What is difficult to parse, however, is
whether the charge order originates among the itinerant electrons or whether
it arises from the ionic lattice. Here we employ high-resolution X-ray
diffraction, combined with high-pressure and low-temperature techniques and
theoretical modelling, to trace the evolution of the ordering wavevector Q in
charge and spin density wave systems at the approach to both thermal and
quantum phase transitions. The non-monotonic behaviour of Q with pressure and
the limiting sinusoidal form of the density wave point to the dominant role of
the itinerant instability in the vicinity of the critical points, with little
influence from the lattice. Fluctuations rather than disorder seem to disrupt
coherence.

\---snip---

So. What does this mean in English? Also, can I downvote my own posts?

~~~
anigbrowl
It is a dense and difficult paper. I've made 5 attempts to summarize what I
think they're saying and deleted them all, which is a reflection of both my
lack of understanding and the difficulty of the underlying concepts.

As best I can make out, they're saying that electromagnetic phenomena depend
more on chaotic subatomic processes than on the purity or exact configuration
of a material's crystalline structure, and they know this because high-
resolution observations at a range of temperatures and pressures correlate
nicely with a particular set of theoretical predictions.

This might be significant in that you could optimize for superconductivity by
tuning the aggregate electromagnetic characteristics of a material rather than
requiring hard-to-achieve structural uniformity at the molecular level.

~~~
selimthegrim
No, they're not subatomic.

Charge density waves mean that there is a periodic modulation of charge (for a
little more background, see the Quora answers here:
[http://www.quora.com/What-are-the-significances-of-charge-
de...](http://www.quora.com/What-are-the-significances-of-charge-density-
waves-CDW-and-spin-density-waves-SDW-in-condensed-matter-physics) and this
pdf: [http://www.wien2k.at/reg_user/textbooks/WIEN2k_lecture-
notes...](http://www.wien2k.at/reg_user/textbooks/WIEN2k_lecture-
notes_2013/magnetism.pdf) ) What they are saying is that itinerant electrons
(those not localized in a given orbital, but which occupy bands throughout the
metallic system and hop, in contrast to an standard insulating magnet) have
the instability within themselves, the lattice does not necessarily need to
give them a push (this is called "dynamically generated"). In my answer I go
into a bit of detail about the heretofore standard role of the lattice as well
as the applications to superconductivity.

What this paper is saying is that the Peierls distortion (cf. answers cited or
Wikipedia) in these systems is either paralleling or a consequence of the
electronic instability. The bit about following the Q wave vector has to do
with the discussion of "nesting" in the answers (that is, how well does the
momentum of the electrons couple with that of the phonons/ionic lattice
vibrations at a certain periodicity and do they steal energy away from the
lattice leading to an overall lower state (and is this the _primary_ factor in
that lowering, a conclusion this paper would seem to militate against)"

A good reference on this is the book by Assa Auerbach "Interacting Electrons
and Quantum Magnetism"

~~~
anigbrowl
I guess subatomic was the wrong word, but we took the same thing away - that
itinerant electrons are inherently unstable rather than being due to a
particular lattice configuration.

Although, insofar as the electrons have the instability within themselves, to
use your words, how is the cause not subatomic? Does it not arise out of some
aspect of the electron's internal structure? Maybe I'm just using it too
loosely.

Thanks for taking the time to explain it properly.

~~~
selimthegrim
It arises from their _collective dynamics_, this is a very important point and
an excellent distinction you are making. It probably has more to do with their
nature as fermions than anything else - see Wikipedia on a Wigner crystal for
a similar phenomenon

