Researchers Demonstrate Heat and Sound Are Magnetic | Hacker News Reader

Researchers Demonstrate Heat and Sound Are Magnetic

spectrum.ieee.org

47 pointsbronz16 comments

I hate to follow the pattern of negative Hacker News comments, but this article is atrocious. Please don't upvote it.

First, the title is total clickbait. Heat and sound are magnetic??? More like heat and sound are affected a little bit by magnetic fields. (Giant magnetic fields at low temperature, no less.)

Second, take a look at the first paragraph:

>"Earlier this month, we reported on research demonstrating that heat propagates as a wave through graphene rather than as vibrations of atoms the way it does in 3-D materials. In 3-D materials, the collective state of those vibrating atoms is known as phonons."

What does it mean to say that heat propagates as a wave rather than as vibrations of atoms? The definition of phonon is a WAVE of ATOMIC VIBRATIONS. It makes zero sense to say it travels as wave, but not as vibrations. Also, there is not a fundamental difference between heat transport in graphene and normal materials - the main difference is that is just takes a longer distance before the wavelike motion scatters enough to become diffusive.

Source: Years of work in a materials science lab on 2D materials and a PhD in Applied Physics

You are correct on all points. I believe the article is trying to refer to the recent studies:

http://www.nature.com/ncomms/2015/150218/ncomms7290/abs/ncom...

http://www.nature.com/ncomms/2015/150306/ncomms7400/full/nco...

Press release from the OSU lab that did the study - http://news.osu.edu/news/2015/03/23/heatmag

Having been taught by both Roberto Myers and Dr. Heremans, they wouldn't release something like this unless they had repeatedly reproduced results and were extremely confident in their findings.

5 degrees above absolute zero, in a 7 tesla magnetic field produces a 12% effect by a completely unexplained and unpredicted mechanism.

I will wait for another researcher to confirm before I get too excited.

your first sentence sounds a lot more exciting than the article title.

As tbrownaw points out elsewhere they apparently do have an explanation and maybe even the ability to predict the behavior.

Essentially this isn't _that_ far away from more common things like paramagnetism and diamagnetism where electron orbitals align with an applied magnetic field and the properties of the material change, except in those cases it's their magnetic properties that change. In this case they're saying the speed at which waves/quasiparticles are transmitted through the material changes.

I'm not fond of the title but it's an interesting idea.

I'm just an amateur, but this doesn't actually seem that surprising.

It's also relevant to the part of the book I'm reading now, which I highly recommend to anyone interested in QED, Electromagnetism, or even just Computer Science.

"The Emperor's New Mind" by Roger Penrose (1989) - http://en.wikipedia.org/wiki/The_Emperor%27s_New_Mind

What I thought the article was about after reading the title here: "Heat and sound are magnetic"

What I thought the article said after reading the article itself: "Heat propagates as a wave rather than as atoms. These waves are called "phonos" (wtf?! #1) and they carry sound too (wtf?! #2)"

What people with knowledge in the field seem to think about the article, judging from the comments: "Total bullshit".

I'd love someone to elaborate with some patience and simple explanation of what this is (and isn't) about because it sure sounds very interesting.

In a damned material! If you have the right terms giving a coupling between the electromagnetic field and phonons, yes, yes that's what happens. No, in free space, there is no such coupling.

We've been in a low-fun aether pocket for a while now- maybe in a few centuries..

Sigh. It is an interesting result, but I expect that you'll find that magnetic constriction of the structural motion has much more to do with heat propagation (or not). If someone liberates the actual paper I would be interested in reading it.

The research group put up a PDF (direct DropBox link is theirs) here:

https://windlgroup.engineering.osu.edu/publications

https://dl.dropboxusercontent.com/u/27852198/WW/Jin_NM_2015....

Cool.

"""The displacements of atoms locally affect the orbital motion of valence band electrons, which, in the presence of an external magnetic field[...]. The process is modelled by ab initio calculations that, without the use of a single adjustable parameter, reproduce the observed 12% decrease in the lattice thermal conductivity[...]"""

Because the bonds between atoms are based on electrons, they can be affected by magnetic fields. Which means that materials can have different properties when exposed to magnetic fields, even if they're not magnetic themselves. We understand this well enough to model it exactly, at least in simple cases.

So ... Val Kilmer in "Real Genius" was right that freezing a liquid laser increases the efficiency, and 30 years ago at that?

http://en.wikipedia.org/wiki/Real_Genius

How is this any different than materials that change color or refractive index based on temperature?

Yeah it's kinda cool, but the interpretation (and title) are ridiculous.

"Semiconductor found to have different physical properties when under strong magnetic field."

makes perfect sense for materials that allow idealised forms of wave propagation to behave like this. Might even make a neat sonoluminescent thingy if you fiddle with it.

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