Molecular Bose-Einstein Condensates: Molecular Dynamics for Polar Molecules with Long-Range Interactions

Molecular Bose–Einstein condensates could be used in myriad ways. One possibility is to create exotic supersolid phases, in which a rigid material flows without resistance. So far this has been achieved only in atomic gases with magnetic interactions — it could now be done in polar molecules, whose interactions are “way stronger”, he says.

Sebastian Will, a physicist at Columbia University in NYC who led the latest work, says that Molecules are more complicated than atoms. They can rotate and vibrate in ways that are impossible for atoms, and polar molecules — which have positively and negatively charged ends — can interact over long ranges through electromagnetic forces. Because these long-range interactions “define the property of matter around us”, a molecular condensate would allow physicists to simulate and understand a much wider array of phenomena, he says.

This system gives researchers the ability to make simulations of exotic quantum phenomena, including the emission of Hawking radiation from a black hole, by using it as a playground. Condensates have been used as quantum sensors and atomic clocks, and even gone into space.

But there’s a catch. “Compared to atoms … molecules are more difficult to control and cool,” says Zoe Yan, a physicist at the University of Chicago in Illinois.

Feshbach complexes have been pulled into condensates before. The last stage of cooling, which turns clouds of them into a condensate, has been disrupted by chemical reactions. Too few of these interactions can be worked with because they cause the molecule to escape the cloud.

Will and his team discovered a way to prevent these particles from colliding, each of them made with one salt and one caesium atom. The team applied two different kinds of microwave fields to the cloud, one to make the molecules rotate and another to make them oscillate. Together these fields oriented the molecules such that they always repelled each other. Will says that this turned out to be crucial.

The physicists will be able to test their predictions about how this strange matter will behave. Will says the team expects to see quantum droplets after tuning the microwave fields so that some interaction between molecule can occur. The team hopes to watch the formation of a crystal by using lasers to confine the condensation in two dimensions. “That’s something that has never been possible,” says Will.

The Nature Podcast on Twitter after the Capitol Storm of 6 January 2021: Evaluating the Effect of a Social Media Intervention on Misinformation Sharing

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The storming of the US Capitol on 6 January 2021 resulted in the social media platform Twitter (now X) rapidly deplatforming 70,000 users deemed to be sharers of misinformation. To evaluate the effect of this intervention, researchers analysed the activity of over 500,000 Twitter users, showing that it reduced the sharing of misinformation, both from the deplatformed users and from those who followed them. Results also suggest that other misinformation traffickers who were not deplatformed left Twitter following the intervention. Together these results show that social media platforms can curb misinformation sharing, although a greater understanding of the efficacy of these actions in different contexts is required.