Moore Foundation grantees at the Massachusetts Institute of Technology and Princeton University have identified a technique to "fingerprint" a Wigner crystal, a solid made of electrons.
By studying its vibrations, the researchers pinpointed the existence of this unusual crystal, which can be used to study other ordered electronic states.
These new findings, led by foundation grantees Raymond Ashoori and Loren Pfeiffer, were published this week in Nature Physics. Pfeiffer is a grantee through the Emergent Phenomena in Quantum Systems initiative and Ashoori is a Special Projects grantee through the foundation's Science Program.
In 1934, Eugene Wigner, a Nobel Prize-winning theoretical physicist, predicted that electrons would enter a new crystalline phase at low densities. Although we typically think of electrons as charge carriers in metals, in rare instances, these particles can solidify into small crystals containing only a few hundred electrons.
Wigner's prediction was grounded in quantum mechanics, which suggests electrons tend to spread out and fill any given volume. However, Wigner realized that when the repulsive interactions between electrons are strong enough, they can overcome this tendency to spread and instead form an ordered structure — what physicists today call a Wigner crystal.
In practice, the Wigner crystal has been difficult to pinpoint. Because the structure is held together only by the weak forces between electrons, they can easily be disturbed by the millions of other electrons and atoms nearby.
Using a spectroscopic technique called pulsed tunneling, which can probe how electrons "tunnel" into insulating phases, Ashoori and Pfeiffer observed a sharp peak that fit to models for vibrations of a Wigner crystal. This peak provides a signature or "fingerprint" of the vibrations of electrons within the crystal.
"The remarkable sharpness of the structure presents strong evidence of the existence of a Wigner crystal with long correlation length," the researchers said.
Read the full article in Nature Physics, and coverage of the team's findings in MIT News here.
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