Team finds elusive quantum transformations near absolute zero

Elusive quantum transformations found near absolute zero
Rendering of the near-perfect crystal structure of the yttrium-aluminum compound used in the study. The 2-dimensional layers of the material allowed the scientists to isolate the ferromagnetic ordering that emerged near absolute zero. Credit: Brookhaven National Laboratory

Heat drives classical phase transitions—think solid, liquid, and gas—but much stranger things can happen when the temperature drops. If phase transitions occur at the coldest temperatures imaginable, where quantum mechanics reigns, subtle fluctuations can dramatically transform a material.

Scientists from the U.S. Department of Energy's Brookhaven National Laboratory and Stony Brook University have explored this frigid landscape of absolute zero to isolate and probe these with unprecedented precision.

"Under these cold conditions, the electronic, magnetic, and thermodynamic performance of metallic materials is defined by these elusive quantum fluctuations," said study coauthor Meigan Aronson, a physicist at Brookhaven Lab and professor at Stony Brook. "For the first time, we have a picture of one of the most fundamental electron states without ambient heat obscuring or complicating those properties."

The scientists explored the onset of ferromagnetism—the same magnetic polarization exploited in advanced electronic devices, electrical motors, and even refrigerator magnets—in a custom-synthesized iron compound as it approached absolute zero.

The research provides new methods to identify and understand novel materials with powerful and unexpected properties, including superconductivity—the ability to conduct electricity with perfect efficiency. The study will be published online Sept. 15, 2014, in the journal Proceedings of the National Academy of Sciences.

"Exposing this quantum phase transition allows us to predict and potentially boost the performance of new materials in practical ways that were previously only theoretical," said study coauthor and Brookhaven Lab physicist Alexei Tsvelik.

Mapping Quantum Landscapes

The presence of heat complicates or overpowers the so-called quantum critical fluctuations, so the scientists conducted experiments at the lowest possible temperatures.

"The laws of thermodynamics make absolute zero unreachable, but the quantum phase transitions can actually be observed at nonzero temperatures," Aronson said. "Even so, in order to deduce the full quantum mechanical nature, we needed to reach temperatures as low as 0.06 Kelvin—much, much colder than liquid helium or even interstellar space."

The researchers used a novel compound of yttrium, iron, and aluminum (YFe2Al10), which they discovered while searching for new superconductors. This layered, metallic material sits poised on the threshold of ferromagnetic order, a key and very rare property.

"Our thermodynamic and magnetic measurements proved that YFe2Al10 becomes ferromagnetic exactly at —a sharp contrast to iron, which is ferromagnetic well above room temperature," Aronson said. "Further, we used magnetic fields to reverse this ferromagnetic order, proving that quantum fluctuations were responsible."

The collaboration produced near-perfect samples to prove that material defects could not impact the results. They were also the first group to prepare YFe2Al10 in single-crystal form, which allowed them to show that the emergent magnetism resided within two-dimensional layers.

"As the ferromagnetism decayed with heat or applied magnetic fields, we used theory to identify the spatial and temporal fluctuations that drove the transition," Tsvelik said. "That fundamental information provides insight into countless other materials."

Quantum Clues to New Materials

The scientists plan to modify the composition of YFe2Al10 so that it becomes ferromagnetic at nonzero temperatures, opening another window onto the relationship between temperature, quantum transitions, and material performance.

"Robust magnetic ordering generally blocks superconductivity, but suppressing this state might achieve the exact balance of needed to realize unconventional superconductivity," Tsvelik said. "It is a matter of great experimental and theoretical interest to isolate these competing quantum interactions that favor magnetism in one case and superconductivity on the other."

Added Aronson, "Having more examples displaying this zero-temperature interplay of superconductivity and magnetism is crucial as we develop a holistic understanding of how these phenomena are related and how we might ultimately control these properties in new generations of materials."


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More information: Quantum critical fluctuations in layered YFe2Al10, PNAS, 2014: www.pnas.org/cgi/doi/10.1073/pnas.1413112111
Citation: Team finds elusive quantum transformations near absolute zero (2014, September 15) retrieved 20 June 2019 from https://phys.org/news/2014-09-team-elusive-quantum-absolute.html
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Sep 15, 2014
Advances such as this illustrate the foolishness of selling off our helium supplies to people who will use that helium to fill party balloons or make their voices sound high and slightly comical. Liquid helium is necessary for the attainment of the lowest possible temperatures, and the Earth's supply of helium is sharply limited.

At the very least, scientific achievements such as the one reported here will teach us much more about the natural world. Quite likely, some of scientific achievements of the type reported here will become the basis of very valuable new technologies. However, the experiments will not be done if the helium is prohibitively expensive or cannot be obtained at all.

KBK
Sep 15, 2014
From the article: "....The laws of thermodynamics...."

There are NO laws in physics, only theories and postulates.

Do I have to bitch slap every mis-trained and mis-educated fool on the planet, so they understand this ultra critical point??

Laws are for punishing people who don't fit agreed upon societal/cultural norms, they have no place in physics, whatsoever.

If you call the theories and posulates of thermodynamics 'law', what you are saying that you will stone to death everyone who finds violation in those 'laws'? The theories of thermodynamics have been broken so many times in the fringe areas of science, that they are absolutely shattered.

And if you run around calling them laws, no one will ever see or understand those all critical moments that have shifted things... and then the new physics is turned away by a group of small minded brutes who desire only to punish those who step out of bounds.

Sounds like religion to me.

Stop using the word law in any aspect of physics.

Sep 16, 2014
Someone sounds bitter they didn't pay any attention in school, distractions like GEET, HHO and ECAT got the better of them.
Hard luck dude.

Sep 16, 2014
There are NO laws in physics, only theories and postulates.

Do I have to bitch slap every mis-trained and mis-educated fool on the planet, so they understand this ultra critical point??
"A scientific law is a statement based on repeated experimental observations that describes some aspect of the universe. A scientific law always applies under the same conditions, and implies that there is a causal relationship involving its elements. Factual and well-confirmed statements like "Mercury is liquid at standard temperature and pressure" are considered too specific to qualify as scientific laws. A central problem in the philosophy of science, going back to David Hume, is that of distinguishing causal relationships (such as those implied by laws) from principles that arise due to constant conjunction."

-I would like to bitch slap idiots who don't know how to use a dictionary.

Sep 16, 2014
And even then, laws are pretty flexible. Really they're just a historical/linguistic anomaly. Hooke's law is a pretty useful approximation, unless you stretch the spring too much. Ohm's law is good... until the resistor heats up too much from the power flowing through it. Newton's law of universal gravitation is really only an approximate effect from a more fundamental reality.

In any event, don't get hung up on the word "law."

Sep 16, 2014
Very cool, however ferromagnetism leads to fluidization in the future.

Sep 16, 2014
Very cool, however ferromagnetism leads to fluidization in the future.

Sep 16, 2014
Arthur Wilton,
Admittedly, we do suffer a limited supply of Helium.
However, the article states that the temps required (absolute 0) are well below Helium's lowest temp. So they, instead, used a "novel compound".
So.... I assume this precluded the necessity of Helium in the process...

Sep 16, 2014
In any event, don't get hung up on the word "law."
If I recall correctly "law" refers to something derived empirically, which might lack rigorous theoretical underpinnings at the time of discovery

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