Synopsis

Squeezing an Electron Crystal

Physics 12, s128
Researchers have determined the energy required to add an electron to a Wigner crystal—an ordered crystalline state made of electrons rather than atoms.
E. Minot/Oregon State University

The Wigner crystal is an elusive beast. Predicted in 1934, this crystal of electrons, which is one of the most strongly correlated states of matter, forms when the electron density is ultralow. But a lack of clean enough systems with that property make it hard to measure. Within the last few months, researchers have imaged its structure. Now another group, led by Vikram Deshpande at the University of Utah, Salt Lake City, has measured the energy required to add an electron to the crystal, a quantity that reveals the interaction strength of the system. Deshpande says that they were happily surprised to finally achieve the result, as it comes after decades of inconclusive measurements by other groups.

The team created a Wigner crystal by adding electrons one by one to a carbon nanotube suspended between two supports and cooled to 1.5 K. By measuring the energy required to add each electron, the team calculated the resulting Wigner crystal’s electronic compressibility, a parameter that characterizes the ordering of electrons in the lattice. Comparing their results to predictions, the team observed the expected decrease in compressibility as electron density increased.

Deshpande says that previous measurements were inconclusive as they were muddied by another effect: changes in the crystal’s size. When an electron is added to a Wigner crystal, the crystal expands. Disentangling the properties of the crystal—like how well its electrons line up in the crystal lattice—from unknown changes in its size was previously undoable. The team overcame this difficulty by repeating the experiment with a range of parameters, such as the length of the carbon nanotubes and their band gap energy.

This research is published in Physical Review Letters.

–Katherine Wright

Katherine Wright is a Senior Editor for Physics.


Subject Areas

Condensed Matter PhysicsQuantum Physics

Related Articles

Real-Time Monitoring of Nanoscale Polarization Switching
Materials Science

Real-Time Monitoring of Nanoscale Polarization Switching

Researchers have visualized the nanoscale jumps in a ferroelectric’s polarization that are thought to play a key role in how well some ferroelectric devices function. Read More »

Rising Above the Quantum Noise
Condensed Matter Physics

Rising Above the Quantum Noise

The control of molecular-level quantum effects in artificial photosynthetic membranes is a powerful tuning knob for optimizing long-range energy transport, according to a theoretical study. Read More »

Spreading Frost Under the Microscope
Condensed Matter Physics

Spreading Frost Under the Microscope

A new imaging technique reveals the effects of humidity on the spread of frost across a micropatterned surface. Read More »

More Articles