'Y-ball' compound yields quantum secrets
Physicists provide theoretical insights on experiment involving a
'strange metal' that could be foundational to next-generation quantum technologies

Date:
March 21, 2023
Source:
Rutgers University
Summary:
Scientists investigating a compound called 'Y-ball' -- which
belongs to a mysterious class of 'strange metals' viewed as
centrally important to next-generation quantum materials -- have
found new ways to probe and understand its behavior.


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FULL STORY ========================================================================== Scientists investigating a compound called "Y-ball" - which belongs to
a mysterious class of "strange metals" viewed as centrally important to
next- generation quantum materials - have found new ways to probe and understand its behavior.


==========================================================================
The results of the experiments, aided by the insights of theoretical
physicists at Rutgers, could play a role in the development of
revolutionary technologies and devices.

"It's likely that that quantum materials will drive the next generation
of technology and that strange metals will be part of that story,"
said Piers Coleman, a Distinguished Professor at the Rutgers Center
for Materials Theory in the Department of Physics and Astronomy at the
Rutgers School of Arts and Sciences and one of the theoreticians involved
in the study. "We know that strange metals like Y-ball exhibit properties
that need to be understood to develop these future applications. We're
pretty sure that understanding this strange metal will give us new ideas
and will help us design and discover new materials." Reporting in the
journal Science, an international team of researchers from Rutgers, the University of Hyogo and the University of Tokyo in Japan, the University
of Cincinnati and Johns Hopkins University described details of electron
motion that provide new insight into the unusual electrical properties
of Y-ball. The material, technically known as the compound YbAlB4,
contains the elements ytterbium, aluminum and boron. It was nicknamed
"Y-ball" by the late Elihu Abrahams, founding director of the Rutgers
Center for Materials Theory.

The experiment revealed unusual fluctuations in the strange metal's
electrical charge. The work is groundbreaking, the researchers said,
because of the novel way the experimenters examined Y-ball, firing gamma
rays at it using a synchrotron, a type of particle accelerator.

The Rutgers team -- including Coleman, fellow physics professor Premala
Chandra and former postdoctoral fellow Yashar Komijani (now an assistant professor at the University of Cincinnati) -- have spent years exploring
the mysteries of strange metals. They do so through the framework
of quantum mechanics, the physical laws governing the realm of the
ultra-small, home of the building blocks of nature such as electrons.

Analyzing the material using a technique known as Mossbauer spectroscopy,
the scientists probed Y-ball with gamma rays, measuring the rate at which
the strange metal's electrical charge fluctuates. In a conventional
metal, as they move, electrons hop in and out of the atoms, causing
their electrical charge to fluctuate, but at a rate that is thousands
of times too fast to be seen by Mossbauer spectroscopy. In this case,
the change happened in a nanosecond, a billionth of a second.

"In the quantum world, a nanosecond is an eternity," said Komijani. "For
a long time, we have been wondering why these fluctuations are actually
so slow." "We reasoned," continued Chandra, "that each time an electron
hops into an ytterbium atom, it stays there long enough to attract the surrounding atoms, causing them to move in and out. This synchronized
dance of the electrons and atoms slows the whole process so that it can
be seen by the Mossbauer." They moved to the next step. "We asked the experimentalists to look for these vibrations," said Komijani, "and
to our delight, they detected them." Coleman explained that when an
electrical current flows through conventional metals, such as copper,
random atomic motion scatters the electrons causing friction called
resistance. As the temperature is raised, the resistance increases in
a complex fashion and at some point it reaches a plateau.

In strange metals such as Y-ball, however, resistance increases linearly
with temperature, a much simpler behavior. In addition, further
contributing to their "strangeness," when Y-ball and other strange
metals are cooled to low temperatures, they often become superconductors, exhibiting no resistance at all.

The materials with the highest superconducting temperatures fall into
this strange family. These metals are thus very important because they
provide the canvas for new forms of electronic matter -- especially
exotic and high temperature superconductivity.

Superconducting materials are expected to be central to the next
generation of quantum technologies because, in eliminating all
electrical resistance, they allow an electric current to flow in a
quantum mechanically synchronized fashion. The researchers see their
work as opening a door to future, perhaps unimaginable possibilities.

"In the 19th century, when people were trying to figure out electricity
and magnetism, they couldn't have imagined the next century, which
was entirely driven by that understanding," Coleman said. "And so,
it's also true today, that when we use the vague phrase 'quantum
materials,' we can't really envisage how it will transform the lives of
our grandchildren."
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========================================================================== Story Source: Materials provided by Rutgers_University. Original written
by Kitta MacPherson.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Hisao Kobayashi, Yui Sakaguchi, Hayato Kitagawa, Momoko Oura, Shugo
Ikeda, Kentaro Kuga, Shintaro Suzuki, Satoru Nakatsuji, Ryo Masuda,
Yasuhiro Kobayashi, Makoto Seto, Yoshitaka Yoda, Kenji Tamasaku,
Yashar Komijani, Premala Chandra, Piers Coleman. Observation of
a critical charge mode in a strange metal. Science, 2023; 379
(6635): 908 DOI: 10.1126/science.abc4787 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230321112646.htm

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