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Bristol physicists break 150-year-old law
http://www.physorg.com ^ | July 20, 2011 | Staff + University of Bristol

Posted on 07/21/2011 6:46:44 AM PDT by Red Badger

A violation of one of the oldest empirical laws of physics has been observed by scientists at the University of Bristol. Their experiments on purple bronze, a metal with unique one-dimensional electronic properties, indicate that it breaks the Wiedemann-Franz Law. This historic discovery is described in a paper published today in Nature Communications.

In 1853, two German physicists, Gustav Wiedemann and Rudolf Franz, studied the thermal conductivity (a measure of a system’s ability to transfer heat) of a number of elemental metals and found that the ratio of the thermal to electrical conductivities was approximately the same for different metals at the same temperature.

The origin of this empirical observation did not become clear however until the discovery of the electron and the advent of quantum physics in the early twentieth century. Electrons have a spin and a charge. When they move through a metal they cause an electrical current because of the moving charge. In addition, the moving electrons also carry heat through the metal but now it is via both the charge and the spin. So a moving electron must carry both heat and charge: that is why the ratio does not vary from metal to metal.

For the past 150-plus years, the Wiedemann-Franz law has proved to be remarkably robust, the ratio varying at most by around 50 per cent amongst the thousands of metallic systems studied.

In 1996, American physicists C. L. Kane and Matthew Fisher made a theoretical prediction that if you confine electrons to individual atomic chains, the Wiedemann-Franz law could be strongly violated. In this one-dimensional world, the electrons split into two distinct components or excitations, one carrying spin but not charge (the spinon), the other carrying charge but not spin (the holon). When the holon encounters an impurity in the chain of atoms it has no choice but for its motion to be reflected. The spinon, on the other hand, has the ability to tunnel through the impurity and then continue along the chain. This means that heat is conducted easily along the chain but charge is not. This gives rise to a violation of the Wiedemann-Franz law that grows with decreasing temperature.

The experimental group, led by Professor Nigel Hussey of the Correlated Electron Systems Group at the University of Bristol, tested this prediction on a purple bronze material comprising atomic chains along which the electrons prefer to travel.

Remarkably, the researchers found that the material conducted heat 100,000 times better than would have been expected if it had obeyed the Wiedemann-Franz law like other metals. Not only does this remarkable capability of this compound to conduct heat have potential from a technological perspective, such unprecedented violation of the Wiedemann-Franz law provides striking evidence for this unusual separation of the spin and charge of an electron in the one-dimensional world.

Professor Hussey said: “One can create purely one-dimensional atomic chains on substrates, or free-standing two-dimensional sheets, like graphene, but in a three-dimensional complex solid, there will always be some residual coupling between individual chains of atoms within the complex that allow the electrons to move in three-dimensional space.

“In this purple bronze, however, nature has conspired to limit this coupling to such an extent that the electrons are effectively confined to individual chains and thus creating a one-dimensional world inside the three-dimensional complex. The goal now is to find a way, for example, using pressure or chemical substitution, to increase the ability of the electrons to hop between adjacent chains and to study the evolution of the spin and charge states as the three-dimensional world is restored within the material.”

More information: ‘Gross violation of the Wiedemann-Franz law in a quasi-one-dimensional conductor’ by Nicholas Wakeham, et al. in Nature Communications

Provided by University of Bristol


TOPICS: Science
KEYWORDS: electronics; energy; metallurgy; physics
This could lead to some really efficient heat exchangers.............
1 posted on 07/21/2011 6:46:46 AM PDT by Red Badger
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To: ShadowAce

Ping!.........


2 posted on 07/21/2011 6:47:22 AM PDT by Red Badger (PEAS in our time? Obama cries PEAS! PEAS! when there is no PEAS!..........................)
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To: Red Badger

Damn, I just ordered an upgraded radiator for my PC cooling system. I wonder when this new metal will be in our cars and our PCs for cooling?


3 posted on 07/21/2011 6:50:36 AM PDT by rarestia (It's time to water the Tree of Liberty.)
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To: Red Badger

does this mean it conducts heat one direction and charge another direction?


4 posted on 07/21/2011 6:52:11 AM PDT by Mr. K (CAPSLOCK! -Unleash the fury! [Palin/Bachman 2012- unbeatable ticket])
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To: Red Badger

The limitation of the heat exchanger is defined by the diffusivity of the fluids, not the barrier.


5 posted on 07/21/2011 6:54:13 AM PDT by Hoodat (Yet in all these things we are more than conquerors through Him who loved us. - (Rom 8:37))
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To: Red Badger

Why would electrical conductivity get in the way of heat exchangers? Copper works pretty well, even though it does conduct electricity.

The bronze merely has high ratio of thermal to electrical conductivity. It doesn’t necessarily have a very high thermal conductivity.


6 posted on 07/21/2011 6:56:07 AM PDT by coloradan (The US has become a banana republic, except without the bananas - or the republic.)
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To: Red Badger

It would have to be something other than bronze to be used in nuclear power plants. Copper alloys are verboten now, and even a lot of fossil plants are getting rid of copper alloys as the copper tends to leach out and foul steam generators and boiler tubes.


7 posted on 07/21/2011 6:58:04 AM PDT by nuke rocketeer (File CONGRESS.SYS corrupted: Re-boot Washington D.C (Y/N)?)
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To: Red Badger

Ping for later. This looks good.


8 posted on 07/21/2011 6:59:02 AM PDT by Upstate NY Guy
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To: Mr. K

Nope. It means it conducts heat in one direction and doesn’t conduct charge hardly at all...


9 posted on 07/21/2011 6:59:57 AM PDT by piytar (The Obama Depression. Say it early, say it often. Why? Because it's TRUE.)
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To: Red Badger

Gravity: It’s Not Just a Good Idea – It’s the Law


10 posted on 07/21/2011 7:00:02 AM PDT by Zeppo ("Happy Pony is on - and I'm NOT missing Happy Pony")
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To: Red Badger

This needs to be outlawed immediately because it might be worse than cow farts in contributing somehow to global warming

11 posted on 07/21/2011 7:00:28 AM PDT by Zakeet (The Wee Wee's real birth certificate got shredded with his Rezko mortgage records)
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To: rarestia

By the time your car is ready for the junk heap and your computer makes a nice conversation piece in your curio cabinet...............


12 posted on 07/21/2011 7:02:32 AM PDT by Red Badger (PEAS in our time? Obama cries PEAS! PEAS! when there is no PEAS!..........................)
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To: Red Badger

I see an immediate market for purple bronze cannons.


13 posted on 07/21/2011 7:03:30 AM PDT by patton (I am sure that I have done dumber things in my life, but at the moment, I am unable to recall them.)
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To: patton

Or purple bronze rifle barrels.................


14 posted on 07/21/2011 7:04:27 AM PDT by Red Badger (PEAS in our time? Obama cries PEAS! PEAS! when there is no PEAS!..........................)
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To: Red Badger
it breaks the Wiedemann-Franz Law.

So... is that just a misdemeanor, or are they going to have to do jail time?

15 posted on 07/21/2011 7:04:46 AM PDT by Thane_Banquo
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To: nuke rocketeer

This research merely proves that they can break this ‘law’ under certain conditions. The metal used was just the beginning. If it can be done with this metal combo, then it most likely can be done with other metal combos as well...................


16 posted on 07/21/2011 7:07:09 AM PDT by Red Badger (PEAS in our time? Obama cries PEAS! PEAS! when there is no PEAS!..........................)
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To: Red Badger
If it can be done with this metal combo, then it most likely can be done with other metal combos as well...................

I think metal combos would not taste very good.


17 posted on 07/21/2011 7:09:53 AM PDT by Thane_Banquo
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To: Red Badger

I always give a shudder over the abuse of the terms ‘law’ ‘theory’ ‘hypothesis’ etc


18 posted on 07/21/2011 7:22:30 AM PDT by reed13k (For evil to triumph it is only necessary for good men to do nothing.)
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To: reed13k

How dare anyone challenge scientific consensus!


19 posted on 07/21/2011 7:30:16 AM PDT by aimhigh
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To: nuke rocketeer

I guess the cupronickel tubes and tubesheets in heat exchangers would be out of the question then. Unfortunately most nuclear plants have dozens of these style of shell and tube heat exchangers in operation. Stainless steel doesn’t conduct heat nearly as well as most copper alloys.

Not to step on your toes or anything, but I built a lot of replacement parts for those heat exchangers.


20 posted on 07/21/2011 7:41:48 AM PDT by factoryrat (We are the producers, the creators. Grow it, mine it, build it.)
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To: Red Badger
They shouldn't have been allowed to do this, as it violated the current scientific consensus.
21 posted on 07/21/2011 7:47:21 AM PDT by SampleMan (If all of the people currently oppressed shared a common geography, bullets would already be flying.)
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To: Red Badger

QUESTION: Why is the Maestro the obvious target in an electrical storm?

ANSWER: He/she is the Conductor.


22 posted on 07/21/2011 7:51:52 AM PDT by xrmusn ((6/98) Hoping your train of thought isn't derailed because of empty boxcars.)
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To: SampleMan

Now, if only we can get some scientists to break that ‘speed of light’ thingy................


23 posted on 07/21/2011 7:52:26 AM PDT by Red Badger (PEAS in our time? Obama cries PEAS! PEAS! when there is no PEAS!..........................)
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To: xrmusn

And he’s holding a rod...................


24 posted on 07/21/2011 7:53:10 AM PDT by Red Badger (PEAS in our time? Obama cries PEAS! PEAS! when there is no PEAS!..........................)
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To: Red Badger

That soon, huh?


25 posted on 07/21/2011 8:08:51 AM PDT by rarestia (It's time to water the Tree of Liberty.)
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To: Red Badger

The article sparked my interest in the “resistance” at different temperatures of purple bronze.

Found a related article here:

http://www.physics.montana.edu/faculty/neumeier/PBV5.pdf

On the Dimensional Crossover in the Purple Bronze Li0.9Mo6O17


26 posted on 07/21/2011 8:31:02 AM PDT by Texas Fossil (Government, even in its best state is but a necessary evil; in its worst state an intolerable one)
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To: Red Badger

Witchraft and heresy! Purple bronze is an abomination. Actually, this could turn out to be a very important discovery. Thanks for posting.


27 posted on 07/21/2011 9:29:03 AM PDT by kwsmith
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To: factoryrat

Who do you work for? TEI? Yuba?


28 posted on 07/21/2011 3:56:32 PM PDT by nuke rocketeer (File CONGRESS.SYS corrupted: Re-boot Washington D.C (Y/N)?)
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To: Red Badger
For the past 150-plus years, the Wiedemann-Franz law has proved to be remarkably robust, the ratio varying at most by around 50 per cent amongst the thousands of metallic systems studied.

Fifty percent wiggle room isn't much of a law.

29 posted on 07/21/2011 4:01:53 PM PDT by Moonman62 (The US has become a government with a country, rather than a country with a government.)
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To: nuke rocketeer

I worked for a supplier that does overhauls and makes replacement legacy parts for the nuclear plants, mostly section III parts, with some balance of plant work thrown in.


30 posted on 07/21/2011 5:59:57 PM PDT by factoryrat (We are the producers, the creators. Grow it, mine it, build it.)
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