Researchers Discover Excitonium - a Weird New Form of Matter

Researchers create a new form of matter, first theorized 50 years ago.

Excitonium, a strange form of matter that was first theorized almost 50 years ago, has now been discovered by researchers. 


What is excitonium? It is a rather exotic condensate that exhibits macroscopic quantum phenomena like a superconductor or a superfluid. It consists of excitons, particles formed from an unlikely pairing of an escaped electron and the hole it leaves behind. The hole actually behaves like a positively-charged particle itself. It attracts an electron and together they form the composite particle known as the exciton.

In their experiments on non-doped crystals of the transition metal dichalcogenide titanium diselenide (1T-TiSe2), the researchers were able to observe the material and its precursor soft plasmon phase, called “the smoking gun” that proves excitonium’s existence. The precursor phase emerges as the material approaches its critical temperature.

The scientists reproduced their results 5 times on different cleaved crystals during the testing, adding more confidence to the study. 

What they achieved in particular is developing a new technique called momentum-resolved electron energy-loss spectroscopy (M-EELS) that is sensitive enough to distinguish the new material from Peierls phase, an unrelated substance that has the same symmetry. 

Professor of Physics Peter Abbamonte (center) works with graduate students Anshul Kogar (right) and Mindy Rak (left) in his laboratory at the Frederick Seitz Materials Research Laboratory. Photo by L. Brian Stauffer, University of Illinois at Urbana-Champaign.

The research was led by Peter Abbamonte from University of Illinois at Urbana-Champaign, working with the graduate students Anshul Kogar and Mindy Rak, and receiving input from colleagues at Illinois, University of California, Berkeley, and University of Amsterdam.

Abbamonte put their discovery in a historical context:

“This result is of cosmic significance,” said Abbamonte. “Ever since the term ‘excitonium’ was coined in the 1960s by Harvard theoretical physicist Bert Halperin, physicists have sought to demonstrate its existence. Theorists have debated whether it would be an insulator, a perfect conductor, or a superfluid—with some convincing arguments on all sides. Since the 1970s, many experimentalists have published evidence of the existence of excitonium, but their findings weren’t definitive proof and could equally have been explained by a conventional structural phase transition.”

An artist's depiction of the collective excitons in an excitonic solid. These excitations are propagating domain walls (yellow) in an ordered solid exciton background (blue). Credit: Peter Abbamonte, University of Illinois at Urbana-Champaign Department of Physics and Frederick Seitz Materials Research Laboratory.

The graduate student Kogar explained that discovering excitonium was not the original aim of the project but they'll take it.

While the discovery gives us a more detailed understanding of another mystery of quantum mechanics, the practical applications of excitonium are currently in a speculative stage.

You can read the team's paper here.

3D printing might save your life one day. It's transforming medicine and health care.

What can 3D printing do for medicine? The "sky is the limit," says Northwell Health researcher Dr. Todd Goldstein.

Northwell Health
Sponsored by Northwell Health
  • Medical professionals are currently using 3D printers to create prosthetics and patient-specific organ models that doctors can use to prepare for surgery.
  • Eventually, scientists hope to print patient-specific organs that can be transplanted safely into the human body.
  • Northwell Health, New York State's largest health care provider, is pioneering 3D printing in medicine in three key ways.
Keep reading Show less

Florida's higher education system ranks best in the nation

A 2019 ranking of all 50 states' education systems shows the Sunshine State serves its college students well.

Politics & Current Affairs
  • Florida may be the butt of many jokes, but its higher education system is second to none.
  • However, the state's PreK-12 education lacks comparatively, giving Massachusetts the top spot for the best education overall.
  • Americans believe their state governments should prioritize education, but much work needs to be done to catch up to other countries.
Keep reading Show less

5 of Albert Einstein's favorite books

Some books had a profound influence on Einstein's thinking and theories.

Getty Images
Culture & Religion
  • Einstein had a large library and was a voracious reader.
  • The famous physicist admitted that some books influenced his thinking.
  • The books he preferred were mostly philosophical and scientific in nature.
Keep reading Show less

Space-faring humans: Why billionaires, not NASA, will get us there

Mega-rich entrepreneurs are taking us where no human being has gone before.

Videos
  • During the first golden era of space exploration, we went to the moon. Then we sort of dropped the ball for 50 years.
  • The problem is space travel is very expensive, especially the way governments do space travel.
  • Because it costs $10,000 to put a pound of anything into orbit around the planet, we need to have an infusion of public and private funds. That's where billionaires such as Elon Musk and Jeff Bezos come into the picture. With their help, we have new energies, new strategies, and new plans to go back into outer space.