Researchers get heavy into superconductors to find out what makes them tick.
DailyTech readers are no strangers to the quantum
mechanical state of metallic matter known as superconductivity. Once cooled
past a certain critical temperature, the electrons in these materials partake
in an irrational phenomenon. They form into pairs, called Cooper pairs, and
flow unhindered carrying current while suffering no loss.
Another characteristic of superconducting materials is that, once past their
critical temperature and switched into a superconducting state, they exclude
any interior magnetic field, also known as the Meissner effect. Magnetism is
typically deadly to superconductors, but recently scientists created a material
that seems to be immune
to its prohibitive interference.
Research being done at the National High Magnetic Field Laboratory has also
provided some insights into the relationship of a material in a superconducting
state and magnetism. By using a high power magnet, the researchers were
able to peer into the inner workings of a superconductor in a conducting state
and get a glimpse of how electrons group up and form Cooper pairs. They also
discovered that there may, in fact, still be some magnetism going on inside
these materials, though whether it was beneficial or detrimental remains to be
seen.
A group of researchers composed of Rutgers professor of physics, Piers Coleman,
graduate student Rebecca Flint and Columbia research scientist Maxim Dzero are
looking into a different kind of superconductor to try to unlock
the secrets of this mysterious quantum hoopla. Most high-temperature
superconductors, high being a relative term at -88 degrees Celsius, are
composed of cuprate-based materials. The Rutgers-Columbia team is using heavy
metal superconductors, with metals like Neptunium and Plutonium, from the
actinide group of metals.
Though the “heavy electron superconductors” do not superconduct at as high a
temperature as copper and iron based materials do, they have a few properties
which may make them desirable as observation materials. First, these heavy
electron superconductors have active electrons in higher orbitals than
traditional high-temperature materials. Because these crucial electrons are in
the f-orbitals of heavy electron superconductors, as opposed to the d-orbitals
of copper/iron superconductors, it may be easier to study and understand their
interactions.
Heavy electron superconductor materials are also easier to make than their
cuprate-based brethren.
One mysterious characteristic of these heavy electron materials is that they
are filled with tiny atomic magnets called “spins.” However, in some of these
materials, rather than interfering with conductance, these spins seem to help
form a more stable Cooper pair. This magnetism, the Rutgers-Columbia group
believes, helps to make a stronger bond between paired electrons which in turn helps
the materials superconduct at higher temperatures.
While the research is underway using these f-orbital heavy metals, the group
hopes to be able to apply their findings to d-orbital conductors, possibly
enabling scientists to further push the boundaries of high-temperature
superconducting.
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