Gizmorama - December 18, 2017
New matter has been discovered! It's excitonium! That's exciting!
Learn about this and more interesting stories from the scientific community in today's issue.
Until Next Time,
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*-- Scientists discover new form of matter, excitonium --*
The existence of excitonium was theorized nearly a half-century ago. But scientists at the University of Illinois at Urbana-Champaign have for the first time proven its existence -- a new form of matter.
Scientists confirmed the existence of excitonium after analyzing crystals belonging to the transition metal dichalcogenide titanium diselenide, or 1T-TiSe2. The new form of matter is a condensate made up of excitons, particles featuring an escaped electron and the gap left behind by its absence.
The odd quantum mechanical pairing among the excitons lends excitonium unique macroscopic quantum properties, similar to the properties of a superconductor or insulating electronic crystal.
Semiconductors feature bands of energy called valence bands. The bands are full of electrons. When electrons on the edge of the valence bands get excited they can jump the energy gap to the neighboring conduction band, a band without electrons. The escaped electron leaves behind a hole.
The hole left behind by the electron takes on a positive charge and attracts the newly escaped electron. Together, the pair form a composite particle, or boson, called an exciton.
Though predicted in theory nearly 50 years ago, scientists have failed until now to directly observe excitonium. Finding the new form of matter was complicated by the fact that its quantum properties appear similar to the Peierls phase, an oscillation of atomic positions measured in a one-dimensional crystal.
Scientists were able to differentiate between the two signatures using a new analysis technique called momentum-resolved electron energy-loss spectroscopy, or M-EELS. The method is especially sensitive to band excitations, allowing the researchers to measure the excitations of low-energy bosonic particles.
Their observations revealed direct observations of a soft plasmon phase in the transition metal, the precursor to exciton condensation and smoking gun scientists needed to confirm the matter's existence.
"This result is of cosmic significance," Peter Abbamonte, physics professor at the University of Illinois, said in a news release. "Ever since the term 'excitonium' was coined in the 1960s by Harvard theoretical physicist Bert Halperin, physicists have sought to demonstrate its existence."
Scientists published their breakthrough discovery in the journal Science.
Researchers believe their new analysis technique could be used to study a variety of other mysterious quantum mechanical signals and theoretical phases.
*-- Juno data offers new insights into Jupiter's Great Red Spot --*
Fresh analysis of data collected by NASA's Juno probe suggests Jupiter's Great Red Spot extends beneath the gas giant's clouds.
The findings -- presented Monday at the American Geophysical Union meeting in New Orleans -- suggest the famous Jovian storm has roots that penetrate some 200 miles into Jupiter's atmosphere.
The revelation was made possible by Juno's Microwave Radiometer.
"Juno's Microwave Radiometer has the unique capability to peer deep below Jupiter's clouds," Michael Janssen, Juno co-investigator from NASA's Jet Propulsion Laboratory, said in a news release. "It is proving to be an excellent instrument to help us get to the bottom of what makes the Great Red Spot so great."
The first scientific results of the Juno mission -- delivered earlier this year -- showed Jupiter to host a multitude of large cyclone-like storms, the Great Red Spot remains the biggest and most famous. It boasts tremendous wind speeds and measures 10,000 miles across, making the storm 1.3 times the width of Earth.
"Juno found that the Great Red Spot's roots go 50 to 100 times deeper than Earth's oceans and are warmer at the base than they are at the top," said Juno co-investigator Andy Ingersoll, a professor of planetary science at Caltech. "Winds are associated with differences in temperature, and the warmth of the spot's base explains the ferocious winds we see at the top of the atmosphere."
The new Juno data also revealed the presence of a previously unknown radiation band near Jupiter's equator. The zone lies just above the atmosphere and is composed of hydrogen, oxygen and sulfur ions racing at almost light speed.
"We didn't think we'd find a new radiation zone that close to the planet," said Heidi Becker, who is leading Juno's radiation monitoring investigation. "We only found it because Juno's unique orbit around Jupiter allows it to get really close to the cloud tops during science collection flybys, and we literally flew through it."
Juno's Jupiter Energetic Particle Detector Instrument also detected large concentrations of high-energy ion in the planet's relativistic electron radiation belt. Scientists aren't yet sure what kind of ions they are or where they come from.
The Juno probe has conducted eight scientific flybys over Jupiter, dipping its trajectory across the gas giant's upper atmosphere. The spacecraft will begin its ninth close pass on Dec. 16.
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