MIT boffins demonstrate NEW form of magnetism

The Register ^ | 21st December 2012 09:47 GMT | Richard Chirgwin

[Ernest_at_the_Beach]

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A state of magnetism predicted in 1987 has been observed for the first time at MIT, with researchers saying that it might one day find applications in storage and communications technologies.

The “one day” is still quite some way off, however, with the researchers only at the very beginning of observing the properties of what’s called a “quantum spin liquid” (QSL).

The properties of a quantum spin liquid are revealed in the spin properties of atoms in a crystal. Rather than settling into a stable state, as happens in ferromagnetic and antiferromagnetic materials, the “spin moment” in a QSL is constantly changing.

MIT's Herbertsmithite crystal

In the familiar compass needle, magnetism comes from the alignment of all spins in the same direction. The second magnetic state, antiferromagnetism, was first proposed in the 1930s. In an antiferromagnetic material, the spin states align in such a way that the overall magnetism is zero, unless energy is applied. This property is exploited in hard drive read heads.

In the new state of magnetism, the magnetic orientation of particles is unable to settle into an ordered state. Instead, they fluctuate constantly, driven by quantum interactions between particles.

QSL only exists in a type of crystal called a kagome lattice. In the material examined in the MIT research, Herbertsmithite (named after its discoverer), copper atoms lie at the corners of triangular structures. Two of the copper atoms are able to align their spins in an “up-down” arrangement – but the third copper atom can’t align with both the others, so it flips between up and down.

The blue regions in the NIST scan of Herbertsmithite show magnetically ordered regions. The green regions are exciting: they're where the spin state is disordered. Image: NIST

To actually observe the QSL, the researchers spent years manufacturing high-purity Herbertsmithite. The test sample was then imaged using the Multi-Axis Crystal Spetrometer (MACS) at the NIST Center for Neutron Research.

In a disordered material, neutrons scatter evenly across the sample. In the QSL sample, some regions scatter neutrons in a way consistent with magnetism – but in other regions the scattering appears disordered (those regions where the atom’s spin fails to settle down).

Wait, there’s more

Along the way, the researchers made another possible discovery as significant as the QSL: they believe they’ve observed fractionalised quantum states.

Quantum states are generally assumed to exist only as whole numbers – after all, the basis of quantum physics is that the quantum is the smallest possible change in state that can exist.

The MIT researchers say that their material exhibits a state with fractionalised excitations: “spinons” whose excited states apparently exist in a contiuum between quantum states. In the MIT release, the researches say observing this “highly controversial idea” is “a remarkable first”.

The research, conducted by professor Young Lee, Tianheng Han (lead author of the paper), and collaborators from MIT, NIST, Maryland University and Johns Hopkins University, is published in Nature (abstract here). ®

[Salamander]

*ping*

[Ernest_at_the_Beach]

Good Grief......here is the shocker:

***********************EXCERPT***************************

Along the way, the researchers made another possible discovery as significant as the QSL: they believe they’ve observed fractionalised quantum states.

Quantum states are generally assumed to exist only as whole numbers – after all, the basis of quantum physics is that the quantum is the smallest possible change in state that can exist.

[myself6]

[techcor]

That is interesting bump.

[Abathar]

He’s just mad because Herbert Smith got to name his discovery Herbertsmithite and so far his Sheldoncooperite isn’t working out for him...

[douginthearmy]

Once again quantum physicists proving that magic exists.

[aimhigh]

magnetism = crystallized gravity.

[bunkerhill7]

“Rather than settling into a stable state, as happens in ferromagnetic and antiferromagnetic materials, the “spin moment” in a QSL is constantly changing.”

nothin new-
The 3rd copper atom is caught betwen the magnetic fields of the other two copper atoms- This effect can be duplicated by a 3rd grader with 3 iron magnets whereby the middle magnet will wobble forever because it can`t make up its mind which way to go,...Nothin` new-

[count-your-change]

Ah...magnetism is attractive...those clever folks!

[zeugma]

Good Grief......here is the shocker:

No doubt. If their observations hold up, that's groundbreaking in a pertty fundamental sense.

[Talisker]

nothin new- The 3rd copper atom is caught betwen the magnetic fields of the other two copper atoms- This effect can be duplicated by a 3rd grader with 3 iron magnets whereby the middle magnet will wobble forever because it can`t make up its mind which way to go,...Nothin` new-

What's new is that this effect is found inside an otherwise uniform liquid crystal, and activated in a controlled manner via electrical excitation.

Other than that, a 3rd grader could do it.

[bunkerhill7]

This has already been done in doped uniform plastics by the Russians in 1983. cf IEEE. They used it in microwave frequencies as a filter.

[BenLurkin]

“QSL only exists in a type of crystal called a kagome lattice. In the material examined in the MIT research, Herbertsmithite (named after its discoverer), copper atoms lie at the corners of triangular structures. Two of the copper atoms are able to align their spins in an “up-down” arrangement – but the third copper atom can’t align with both the others, so it flips between up and down.”

http://www.moviesoundclips.net/download.php?id=2852&ft=wav

[SunkenCiv]

Thanks Ernest!

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[SunkenCiv]

Thanks Ernest!

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[steve86]

You mean quantum states are analog? So future quantum wall clocks can still have hands?

[TheOldLady]

You already have all the magnetism that you will every need, Mr. Civilizations.

[AFPhys]

“Quantum states are generally assumed to exist only as whole numbers – after all, the basis of quantum physics is that the quantum is the smallest possible change in state that can exist.”

-—<>-—<>-—<>-—<>-—<>-—

This is not totally accurate, and is widely misquoted and misunderstood. It is true for simple systems.

When a system is not a classic “energy well”, the idea of quantum state being integer multiples of the ground state is not accurate; and of course, the further the system goes from being “ideal”, the less constrained and the further from integer multiple becomes evident.

If that were not true, semiconductor switching (for example) would be much more precise, voltages would transition perfectly sharply, and that is a pretty darned ideal system.

The existence of fractionalized states has been long known - example is “spins” of some elementary particles, and even the 1/3 charge of quarks, and I recall seeing some theoretical constructs.

It has been 20 years since I’ve studied/taught this, so I can’t go into much detail about this without a lot of study and thought (and writing time).