flux quantization

A layered cake of molybdenum disulfide MoS2 sits on the lab bench. It is prepared in the usual way: adhesive tape peels off the top layers to obtain a thin sample. But beneath the tape remains an invisible cavity where the atomic floors are no longer pressed together. It is there that electrons begin to behave differently than in the crystal bulk.

A translator who used to catch only fragments of sentences now hears the entire conversation. Similarly, physicists studying strong interactions have long been unable to calculate how two particles respond to a flash of light when they do not form a stable nucleus.

A thin layer of indium arsenide lies hidden under a superconducting film, like a voice beneath the noise of a crowd. In such a hybrid, current takes the path of least resistance and flows almost entirely through the metal, leaving the semiconductor inaudible to standard probes.

In a quiet room with no magnets anywhere, two electrons in a silicon trap still feel a faint trembling. It comes from the nuclei of silicon and germanium atoms, which spin randomly like the needles of broken compasses. This trembling was once considered noise, but now it has become a measuring instrument itself.

A thin film of zirconium nitride lies on a magnesium oxide substrate. Its thickness is two-tenths of a micron, like a spider's web, but inside it quantum life is boiling. When cooled to half a kelvin, superconductivity does not disappear all at once: it breaks up into rare islands that still hold on amid the disorder.

In a narrow corridor, people walk in rows rather than as a crowd. The number of rows depends on the width of the passage. In graphene, this corridor is a quantum point contact — a constriction where electrons move ballistically without scattering.

A superconducting quantum interferometer is a device that senses magnetic fields billions of times weaker than the needle of an ordinary compass. Inside it, there is a narrow bridge where superconductivity briefly breaks.

A superfluid gas is like a crowd of people marching in step: each atom knows where to go and doesn't fall out of the common rhythm. But this crowd has three 'valleys'—three different directions it can take. In a new experiment, physicists made one valley slightly more 'favorable' than the others and watched how the crowd darted between them.

In a dark room, a whisper is barely audible. To make out the words, you need to get close, or set up many sensitive microphones. That's roughly the reasoning behind the new work: the authors place quantum "ears" right inside a resonator, where a high-frequency gravitational wave turns into an electromagnetic echo.

Two sheets of tungsten diselenide (not carbon, but a compound of tungsten and selenium) are rotated relative to each other by a tiny angle, about 5 degrees. This creates a moiré pattern: an enlarged periodic lattice where electrons behave very differently than in a regular crystal.

After the Big Bang, according to inflationary cosmology, the Universe underwent rapid expansion and a series of phase transitions.

In the quantum world, there is its own dance. Two superconducting toroids, each comfortably holding its quantized magnetic flux, whirl in a synchronous waltz. Between them is a vacuum, not a single field line, yet they mirror each other’s moves without fail.

Spintronics promises to transmit information not by charge but by spin, ridding microelectronics of its main enemy — Joule heating.

Superconductivity and magnetic field are age-old foes: the field barges in like a whirlwind, tearing apart the delicate pairing of Cooper pairs, destroying order.

Two-dimensional worlds never cease to amaze: here even crystal melting is not a symmetry breaking but a vortex drama discovered by Kosterlitz and Thouless. At the heart of this theater are topological сингулярности, whose energy and энтропия bargain for order. This language is common to сверхтекучести и сверхпроводимости.

A well-coordinated orchestra of electrons in a superconductor is easily thrown off rhythm. Thermal jolts destroy the fragile order, and resistance returns. For decades, scientists have sought ways to strengthen this ensemble — mostly by changing the material's composition or compressing it to unimaginable pressures.

A long pipe with a wave rolling along it. From far away, the pipe looks like just a line — one dimension has vanished. That's roughly how physicists get from an 11-dimensional theory of gravity (which describes everything: particles and forces alike) down to 10 dimensions. They take one dimension and close it into a tiny ring, invisible at large scales.

Electrons in a conductor are like a chaotic crowd: colliding, they lose energy, and resistance arises. In a superconductor, however, they move in unison, like partners in a well-coordinated dance, without touching each other. This state has reduced энтропией — meaning disorder. Such behavior is rare for gold and copper.

A long, narrow pan, and a thin pancake sets in uneven stripes. For decades, scientists saw a similar picture when modeling the behavior of electrons in superconductors — materials that conduct electricity without loss. They used elongated "cylinders," and the result was always the same: rigid magnetic "stripes" that were thought to hinder superconductivity.

In superfluid helium, friction disappears — the liquid flows like a mountain stream, but without a single eddy. A short laser pulse rippled this smooth surface, and scientists using spectroscopy captured the spreading ripples — quantum waves with many speeds.

A black hole, perturbed by a merger, vibrates at characteristic resonant frequencies — much like a bell ringing after being struck. Each hole has its own spectrum of these oscillations, allowing astronomers to reconstruct its parameters.

A magnetic field penetrates a superconductor not as a continuous flux but as thin filaments — vortices. Usually, they repel each other and arrange into a neat triangular lattice, like floats on water. But in CaSb₂, things went differently: vortices bunched into tight clusters, with almost empty space between them.

Inside a superconductor, a magnetic field typically twists into tubes, vortices, each carrying one quantum of magnetic flux. That's how the classic Abrikosov lattice works. But in LiFeAs crystals, the picture is different. Muon spectroscopy showed that the field penetrates not as individual vortices but as stripes. Each stripe contains pairs of 'coreless' vortices.

Physicists are trying to hear a whisper in a noisy room. They build a soundproof booth, but even inside, their own breathing and heartbeat create interference. That's roughly how the search for quantum gravity goes: they want to see gravity bind two particles into a single whole — entangle them.

A superfluid gas behaves like a frictionless liquid. Two clouds of such gas are connected by a narrow bridge, and a stream of particles flows through it. This resembles the Josephson effect in superconductors, but here the particles are neutral atoms instead of electrons.

Magnetic sensors smaller than a match head can already detect weak fields — from a beating heart or a distant planet. But making them even more sensitive involves a trade-off: improve one part, and you lose performance in another.

Ordinary magnetic measurements only see the surface of a superconductor, where barriers and viscous flows of magnetic field get in the way. Inside, in the so-called intermediate state, superconducting and normal domains coexist, separated by thin walls. These walls can oscillate, but hearing them directly has been difficult.

In superfluid helium, a vortex is like a tornado in a bottle, but instead of water, it's a quantum liquid that flows without friction. Such a vortex doesn't dissipate on its own, so the question of where its energy goes has long remained open.

A single electron in a magnetic field is like a tiny top that spins and weakly "squeaks" at its own frequency. Hearing that squeak directly is nearly impossible: it gets lost in the noise. Scientists have devised a resonator: a superconducting microwave strip that works like a tuning fork tuned to the same note.

A magnetar is a neutron star with a magnetic field hundreds of millions of times stronger than Earth's. If you brought an ordinary magnet near such a field, it would instantly lose its magnetism, and atoms would stretch into thin filaments.

A thin sheet of graphene, just a few micrometers thick, was placed in a weak magnetic field, and it began to push the field out of itself, like a sponge squeezing out water. This effect, known as the Meissner effect, is the hallmark of a superconductor: a material that conducts electricity without loss.

Electric current in a superconductor is like a crowd running down a frictionless corridor. But in type-II superconductors there are obstacles, tiny vortices of magnetic field, that the current shoves out of place. Once a vortex moves, resistance appears and the current drops.

Magnetic atoms in a solid are like compass needles: usually, when cooled, they align in one direction: that's how magnetism arises. But in TbInO3, the terbium needles sit on a triangular lattice where it's impossible to please all neighbors at once. One needle wants to point north, another south, and in the end none can settle into a stable position.

The surface of the uranium compound UTe2 crystal looks like a frozen sea: in some places, electrons move freely; in others, they get stuck near atoms. A scanning tunneling microscope, a device that probes the surface with an atomically sharp tip and senses individual electrons, revealed that this landscape is not random.

An ordinary superconductor expels magnetic fields, but this ring does the opposite: it creates a magnetic field inside itself. The ring is made of Fe(Te,Se) — a compound of iron, tellurium, and selenium that loses its electrical resistance at very low temperatures.

A superconductor carries current without loss, like a perfectly smooth road where cars glide with no friction. But what if you scatter rocks and potholes across that road? Scientists decided to find out by adding disorder to a superconducting material just one atom thick.

The quantum Hall effect has long been suspected of superfluidity — the ability to flow without friction. Imagine a cook following a recipe: for each unit of magnetic flux, he must add exactly a certain number of electrons.

Liquid helium at ultra-low temperatures enters a state of superfluidity: it flows without friction, like a perfect lubricant.

A fridge magnet sticks because the tiny atomic arrows inside it are aligned in one direction. But quantum mechanics makes these arrows jitter, so the overall magnetization falls short of the ideal.

An ordinary ultra-sensitive magnetic field sensor is like a scale that starts lying when you put too heavy a weight on it. The signal becomes distorted, and you have to add complex electronics to straighten out the readings. That electronics adds noise and slows things down. The new sensor, bi-SQUIPT, works differently.