Scientists Capture Images of Electron Molecular Crystals

Researchers from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, the University of California at Berkeley, the Massachusetts Institute of Technology, Arizona State University, and the National Institute for Materials Science in Tsukuba, Japan, have captured direct images of a new quantum phase of an electron solid – the Wigner molecular crystal. Whereas Wigner crystals are characterized by a honeycomb arrangement of electrons, Wigner molecular crystals have a highly ordered pattern of artificial “molecules” made of two or more electrons. The scientists formed a nanomaterial, called a “twisted tungsten disulfide moiré superlattice,” and doped it with electrons, which filled each 10-nanometer-wide unit cell of the material with just two or three electrons. In a surprising result, these filled unit cells formed an array of moiré electron molecules throughout the superlattice – resulting in a Wigner molecular crystal.