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Imaging the electronic Wigner crystal in one dimension

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Science  31 May 2019:
Vol. 364, Issue 6443, pp. 870-875
DOI: 10.1126/science.aat0905

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Visualizing a tiny crystal

Electrons repel each other. When confined to a small space, electrons can form an ordered, crystalline state called the Wigner crystal. Observing this fragile crystal is tricky because it requires extreme conditions—low temperatures and densities—and very noninvasive probes. Shapir et al. created such conditions in a carbon nanotube, which housed the electrons, and a second nanotube that scanned the first nanotube, serving as a probe. The measured electronic densities were consistent with theoretical predictions for small Wigner crystals of up to six electrons in one dimension.

Science, this issue p. 870

Abstract

The quantum crystal of electrons, predicted more than 80 years ago by Eugene Wigner, remains one of the most elusive states of matter. In this study, we observed the one-dimensional Wigner crystal directly by imaging its charge density in real space. To image, with minimal invasiveness, the many-body electronic density of a carbon nanotube, we used another nanotube as a scanning-charge perturbation. The images we obtained of a few electrons confined in one dimension match the theoretical predictions for strongly interacting crystals. The quantum nature of the crystal emerges in the observed collective tunneling through a potential barrier. These experiments provide the direct evidence for the formation of small Wigner crystals and open the way for studying other fragile interacting states by imaging their many-body density in real space.

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