supercooling

A tiny black hole flies through a hydrogen cloud and stretches atoms like taffy. That is what a superconductor looks like when it traps a persistent current: a material in which electricity flows without losses turns into a miniature permanent magnet.

Instead of an ice bath, a warm gas blanket. That is how the cryogenic current comparator at Japan's National Metrology Institute is now cooled. Previously, this instrument, which compares electric currents to within billionths of a percent, required immersion in liquid helium.

Molecules in an ultracold gas are like tiny magnets: they attract when far apart, but when they get close they can stick together for good. Such sticking destroys the gas: particles drop out of the game, and you never reach the quantum regime where all of them behave as one.

In the depths of sub-Neptunes, the most common type of planet in the Galaxy, though not one you could stand on, silicate magma and hydrogen mix into a single supercritical cocktail. Previously, it was thought that beneath the dense hydrogen atmosphere lay a sharp boundary with molten silicate, like oil on water.

A quantum lab is like a kitchen where the chef waits a day for the stove to cool down. Superconducting qubits only work at temperatures of a few hundredths of a kelvin, and each 'cool, measure, warm up' cycle eats a whole day. A team of engineers built a fridge the size of a melon, weighing 3 kg, that does the job in just two hours.

Inside a diamond anvil cell, squeezing a sample with a force millions of times greater than atmospheric pressure, a thin film of lanthanum meets hydrogen. The hydrogen comes from ammonia borane — a powder that, when heated, releases its hydrogen like a sponge releasing water.

An ordinary wire heats up when current flows through it — some energy is wasted. A superconductor lacks this flaw: electricity flows through it without loss, like water through a perfectly smooth pipe. The trouble is that most superconductors require either very low temperatures or colossal pressures, like those found in the depths of planets.

Quantum computers make mistakes. Each qubit is like a ball balanced on the tip of a pencil: a slight tremor in the hand and it rolls off. To keep the balls from falling, you need someone to notice the wobble and correct it in time.

A film sliver thinner than a human hair was placed between diamond anvils and squeezed. The pressure climbed — a hundred thousand atmospheres, half a million, a million… Yet the material kept conducting electricity without resistance.

A laser beam can do more than heat things up: it can also calm motion. When light enters a mirror trap, it exerts pressure on the mirrors, and if you tune the beam's color just right, that pressure becomes a gentle braking force. This is how tiny mechanical vibrations are cooled to nearly absolute zero.

A pot of extremely thick and hot glue: that's roughly what the early Universe looked like. It wasn't ordinary glue, but a 'gluon soup': particles carrying the strong force (gluons) zipped freely through space. The temperature was so high that even quarks and gluons didn't stick together into protons and neutrons. Over time, the Universe cooled.

A piece of metal is cooled to minus two hundred degrees, and electric current begins to flow through it without the slightest friction, like water in a pipe flowing without touching the walls. This behavior is called superconductivity.

Dark matter is the invisible scaffold that holds galaxies together. But how did it come to be? The standard answer: particles of dark matter once stopped colliding and "froze out" in the amount we see today. However, there's a trickier path — UFO, or ultra-fast freeze-out. Here, everything is like coffee that cools down and then heats up again as you carry it through a cold corridor.

Usually, superconductivity is a story about cold. The lower the temperature, the easier it is for electrons to pair up and flow without resistance. But in a new study, physicists grew thin films of nickelates doped with europium and saw the opposite picture.

A thin film of yttrium barium copper oxide warms under a stream of infrared light, and suddenly stops dissipating energy. That's superconductivity: electrons pair up and move as a single quantum swarm. But in underdoped samples, the harmony breaks long before the pairs fall apart. The pairs are there, but the collective rhythm isn't.

A hot liquid flows easily: molecules dart around, collide, and quickly find new spots. But cool it below its freezing point, and everything changes. Motion nearly freezes, and viscosity skyrockets. The key question isn't that particles are lazy, but where they can even go. The authors combined two established ideas.

If you squeeze water between two glass plates so that only two layers of molecules fit, it becomes something between a liquid and ice. At room temperature, molecules in such a trap still move but arrange themselves into a semblance of a crystal lattice.

Two white sheets lie in the sun — one rough, one smooth. Which one heats up less? The rough one scatters light more strongly, so it seems it would stay cooler. But if the coating is made of many transparent glass beads, the logic changes. Light wanders through it like in a thick fog, and at some point it stops noticing individual droplets.

Imagine a sandwich where the bread is made of copper oxide layers and the filling is a thin layer of strontium ions. That's the infinite-layer cuprate, the simplest version of superconducting ceramics, conceived nearly 40 years ago.

Hot tea in a freezer doesn't freeze all at once. First, tiny ice needles dart around — forming and melting until the temperature drops enough for the ice to set solid. The early universe behaved similarly as it cooled and changed its internal structure.

A black hole is like an ember that was thought to smolder forever, but eventually must go out — evaporating without a trace.

Imagine a packed dance floor where dancers glide without any friction — passing through each other without a touch. That's a superfluid. In a neutron star's crust, neutrons could behave this way, but a rigid lattice of ions gets in the way, like suddenly sticking the dance floor full of pillars.

A tiny ball weighing a fraction of a milligram, suspended in a magnetic field and cooled to near absolute zero, oscillates for 110 hours without stopping: this is record isolation. The energy loss is so small that the system's entropy barely increases, making any external influence noticeable.

A chef pours hot sugar syrup onto a cold table, and it sets into crystals. That's roughly how engineers pictured metal solidification: the liquid instantly becomes a scatter of crystalline grains. But close-up imaging revealed an extra stage wedged between liquid and solid.

A pot of water on the stove: the hotter the burner, the faster ice turns to water, and water to steam. Heat destroys order. But sometimes nature pulls a trick, and heating makes a liquid freeze, like a puddle turning to ice on a frosty morning.

Plutonium is a metal with attitude. One form shrinks when cooled, another swells. But at room temperature, the alloy behaves strangely: the ruler says one thing, X-rays say another. The ruler shows the sample barely grows, while X-rays see atoms in the crystal lattice moving further apart.

Inside copper-based superconductors, materials that carry current without loss at unexpectedly high temperatures, there is a hidden phase. It behaves like an ordinary metal, but it's invisible in standard measurements.

A copper crystal is squeezed in diamond anvil cells. As pressure mounts, a battle unfolds inside the material between two states: one prepares electrons for superconductivity, the other hinders their pairing. Scientists tracked this struggle using ultrashort laser pulses.

Imagine trying to examine a snowflake without letting it melt or get damaged. That's roughly the challenge facing scientists who want to study individual proteins — the tiny molecular machines of life. In solution, a protein constantly jiggles and clumps with its neighbors, and in an electron microscope, the beam destroys it.

Two tiny dust grains hover at the crossing of laser beams. Each is held by its own 'tweezer'—a focused beam that keeps the particle from falling. Inside a mirrored cavity, light bounces between the walls, and its oscillations are coupled to the trembling of the grains.

An ordinary aluminum pot on a stove doesn't emit molecules you can catch with light. But if you take aluminum and an aluminum salt, heat them together in a small oven, you get a stream of aluminum fluoride molecules, like steam from a kettle's spout, except instead of water droplets, tiny particles fly out.

A metal needle descends onto a piece of superconductor. All of this happens inside a refrigerator that cools the sample to 30 thousandths of a degree above absolute zero — a hundred times colder than outer space. A weak current is passed through the needle, and by how electrons travel through the tiny contact point, physicists read what is happening inside the material.

In helium cooled to near absolute zero, the liquid stops rubbing against itself and begins to flow without any resistance.

Lasers usually heat things up. But in some crystals, light can carry heat away, like a teapot cooling under a bright lamp. In diamond, this job falls to defects: spots where a nitrogen atom replaces carbon, with a vacancy nearby.

Water is the only common liquid that doesn't immediately contract when cooled. Ice melts, and water becomes denser, but only up to 4 degrees Celsius. Beyond that, with further cooling, it expands again. This quirk explains why fish survive in freezing ponds: the densest water sinks to the bottom, while a lighter cold layer stays on top and turns into ice.

A neutron star is the dead core of a star that once exploded, compressed to the size of a city. If a normal star is nearby, the neutron star siphons matter from it like a vacuum cleaner. This matter falls onto the surface and forms a crust — a solid layer of neutron-rich atomic nuclei.

Hydrogen is a champion in energy per kilogram, but storing it is a hassle. As a gas, it takes up a huge volume, and if you compress it or cool it to a liquid, you need heavy tanks and lots of energy. There's a third way: some solid materials absorb hydrogen like a sponge soaks up water and hold it within. Heat it up, hydrogen comes out; cool it down, it gets absorbed back.

Ice slips away from under a skate blade like a bar of soap in wet hands. For a hundred years, scientists argued about where this slipperiness comes from. Some said there is already a thin layer of water on top: it acts as a lubricant. Others countered that water only appears when you start moving, due to friction.

Superconductivity is the ability of a material to conduct electricity without losses. Ordinary wires heat up, and some energy is lost as heat, but a superconductor carries current with zero resistance.

Quantum materials are like finicky flowers: they only bloom in the cold. At room temperature, they hide their unusual properties, but when deeply cooled, they become superconductors or change their magnetic behavior. To understand how they work, you need to examine their atoms in the very cold where these properties reside.