Supersolidity Is Born at the Liquid Boundary ⚡ экспресс
Scientists have discovered that a 'supersolid' state can spontaneously appear at the boundary between a superfluid liquid and a solid—as if water near the shore froze into a pattern but kept flowing without friction. This works for various liquids and doesn’t require changing their internal properties. This 'quantum crust' paves the way for new devices. One wonders what surprises it might still hold.
A supersolid is ice that flows. Think of a pond with a frozen crust, but beneath it, a liquid depth without friction. Usually, creating that crust means changing the liquid's properties throughout its entire volume. A team of researchers studying liquid helium found a simpler way: they made the surface vibrate with special waves, and the liquid grew its own solid 'skin.'
Those vibrations weren't just ordinary ripples—they were quantum whirlpools called rotons, whose nature was uncovered by Feynman. By coupling with the motion, they order the atoms at the boundary into a crystal. In Bose–Einstein condensates, a similar effect occurs when the wavelength matches the trap size. The result is a material whose surface holds its shape while the inside flows freely. It’s possible that similar processes harden the crust of neutron stars.
🎯 The idea of supersolidity is over half a century old, but it wasn’t until 2017 that it was realized by trapping ultracold atoms in a laser cage.