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Example of large-scale mapping of moiré superlattice, lateral PFM image.

Scanning reveals two view of the structure of a superlattice formed from layers that are each one atom thick. Credit: L.J. McGilly et al./Nature Nanotechnol.

Physics

A snapshot shows off super-material only two atoms thick

High-powered microscope allows scientists to visualize an exotic structure called a superlattice.

A widely used type of microscopy can reveal the structure of 2D ‘wonder materials’ in superb detail.

Take two carbon sheets, each only one atom thick. Stack them, then rotate them so that their crystal structures are slightly misaligned. The resulting structure, called a ‘twisted bilayer’, can have surprising properties, such as superconductivity, making this and similar structures of great interest to physicists.

To image a type of twisted bilayer called a superlattice, Abhay Pasupathy at Columbia University in New York City and his collaborators used a room-temperature technique that applies alternating electric fields to a material, creating slight changes in the material’s surface. A fine probe detects these changes to reveal the material’s topography.

The bilayer contains tile-shaped regions where its two crystalline sheets are close to an energetically favourable alignment. Interesting physics arises from the interaction between the tiles and the material’s electrons — but the details have been inaccessible to scientists relying on more-standard forms of room-temperature microscopy, which typically cannot image the tiles.

The new method not only reveals the tiles but shows, unexpectedly, that the electrons in the material move to the edges of the tiles.

More Research Highlights...

Plastic and other debris floats underwater in blue water

Plastic detritus from snacks and meals floats in the Red Sea. Marine sampling shows that food waste accounts for nearly 90% of plastic pollution at some locales. Credit: Andrey Nekrasov/Barcroft Media/Getty

Ocean sciences

Humanity’s fast-food habit is filling the ocean with plastic

Food bags, drink bottles and similar items account for the biggest share of plastic waste near the shore.
Conceptual artwork of a pair of entangled quantum particles.

An artist’s impression of ‘entangled’ particles, which share properties even at a distance. Entangled photons can be used to help secure a multi-party video meeting. Credit: Mark Garlick/Science Photo Library

Quantum information

Quantum keys dial up tamper-proof conference calls

A new experiment efficiently distributes the highly secure keys to four parties instead of the typical two.
Farmers harvest pineapples in a field.

Workers harvest pineapples in Lingao County, China. Less than one-third of the money spent on food eaten at home reaches farmers. Credit: Yuan Chen/VCG/Getty

Economics

Poor harvest: farmers earn a pitiful fraction of the money spent on food

The bulk of consumer food spending around the world ends up in the coffers of distributors, processors and other parties beyond the farm gate.
A woman wearing a protective face mask splashes her hands in a jet of water

A pedestrian seeks relief from searing temperatures in Spain, where a high proportion of heat-related deaths have been linked to climate change. Credit: SALAS/EPA-EFE/Shutterstock

Climate change

More than one-third of heat deaths blamed on climate change

Warming resulting from human activities accounts for a high percentage of heat-related deaths, especially in southern Asia and South America.
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