proximity effect

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 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.

An empty dance floor where people occasionally appear. Each moves on their own, chaotically, with no connection to the others. But when the right music starts and the hall cools down a bit, the dancers suddenly begin to form long chains and move in unison. That's roughly how electrons behave in a dilute three-dimensional gas.

A quantum spin liquid is a state of matter in which the magnetic moments of atoms behave like a fluid: they constantly fluctuate and never settle into a rigid order, even at extremely low temperatures. One of the most famous theoretical models of such a liquid was proposed by Alexei Kitaev.

Many materials behave like finicky ice: at one pressure they melt, at another they turn harder. Superconductors in the cuprate family are no exception. Their ability to carry current without loss depends on how tightly the crystal lattice is squeezed. In a new study, physicists traced this dependence for the compound Bi-2223.

A ceramic plate as thin as a soap film, and through it flows current with zero resistance. That's the superconductivity achieved in nickelates, relatives of the famous cuprate superconductors. Previously, this required enormous pressure, comparable to that at the ocean floor.

Lossless current is the dream of energy technology. Some materials become superconductors, but usually only at extreme cold. Recently, in the family of nickelates, compounds based on nickel, candidates were found that work at higher temperatures.

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.

A thin film of a special crystal (for instance, molybdenum disulfide) sits on a microscope stage. The temperature is just above the point where the material becomes a superconductor.

For nearly forty years, high-temperature superconductivity in cuprates has remained one of the deepest riddles of condensed matter physics.

Graphene, a two-dimensional carbon crystal, has long tantalized physicists with the hope of high-temperature superconductivity. Its electrons obey the relativistic equation of Paul Dirac, racing at tremendous speed, barely noticing each other.

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 switch that knows which way to let current flow. That's how a Josephson diode works — a superconducting bridge where current goes willingly in one direction but meets resistance in the other. In the new study, such a bridge was made from graphene — a sheet of carbon just one atom thick.

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.

In some materials, electric current can flow without any loss: this is superconductivity. But before becoming a superconductor, a substance often passes through a strange state: electrons already sense each other and form pairs, yet they cannot move in unison.

Superconductors conduct current without loss, but usually require extreme cold. Hg1223 — a mixture of mercury, barium, calcium, copper and oxygen — breaks the rule: it stops resisting current already at –139°C. The secret is that the strong electrical repulsion between electrons forces them to pair up.

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 superconductor carries current without resistance, like water running through a pipe without friction. The secret lies in electron pairs: two electrons stick together as one, even though they normally repel. In an ordinary superconductor, the spins of the electrons in a pair point in opposite directions: this is the singlet state.

A bridge made of two rows of planks bends under the feet of pedestrians, and each step gets a boost from the elastic motion of the deck. A similar principle underlies superconductivity: electrons glide without resistance because the atomic lattice itself adapts to them. In nickel-based materials, this picture has long been elusive.

The dance floor is full of couples waltzing. Usually, partners move in opposite directions: one steps forward, the other backward, to keep the overall rhythm.

In the world of superconductors, electrons don't like to be alone. They typically pair up into Cooper pairs and move without resistance, like figure skaters holding hands. But you can make them dance in fours. The authors of this work propose a scheme where Cooper quartets, groups of four electrons exchanging partners in a rapid rhythm, are born.

Superconductivity is when electric current flows without losses, like water through a perfectly smooth pipe. It usually occurs at very low temperatures, but there are materials where it appears at higher ones.

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.

Superconducting circuits often rely on Josephson junctions — places where current flows without resistance through a thin barrier. Typically, this barrier is an oxide layer, but its properties are hard to control at the nanoscale. In this new work, the barrier is a thin layer of niobium or titanium nitride sandwiched between niobium layers.

A piece of silver antimony telluride is like a sponge: it readily soaks up heat and turns it into electricity. Such materials are called thermoelectrics, and they already work in space probes and car refrigerators. But if you squeeze this sponge, it starts behaving like a superconductor — current flows with zero resistance.

Certain materials, near absolute zero, superconduct: electricity flows without loss. The critical temperature starts this. John Bardeen and colleagues explained that atomic vibrations glue electrons into Cooper pairs.

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.

A thin film of indium arsenide on an insulating substrate behaves like a double-walled thermos: the electrons inside barely give off heat to the surrounding crystal. In an ordinary metal, electrons quickly exchange energy with atomic vibrations, so their temperature is always close to that of the sample.

An ordinary conductor carries current equally in both directions, like a door that swings both inward and outward. A diode, by contrast, is a door with a self-closing hinge: it opens easily one way but pushes back the other.

An ordinary superconductor is like a squad of soldiers marching in pairs: electrons pair up, and their spins (internal 'tops') point in opposite directions. A magnetic field easily flips such pairs, destroying superconductivity. In UTe₂, things are different.

In a thick metal, electrons are like a discordant orchestra: each instrument plays on its own, the overall sound is noise. But roll the metal into a film just a couple of atoms thick, and electrons suddenly begin to "play" in harmony, conducting current without dissonance. Even John Bardeen explained that in superconductors, electrons form pairs — duets that move unimpeded.

Light from many tiny emitters — atoms or artificial "quantum dots"—usually scatters in all directions, like a crowd where everyone shouts on their own. But if you make them "sing in chorus," the flash becomes many times brighter.

An ordinary superconductor works only in nature's freezer — at temperatures below minus one hundred degrees. The carbon-ball material K₃C₆₀ is no exception: without cold, it resists current like a crowd in a narrow corridor. But physicists noticed something strange: if you shine a laser on it, it starts conducting without loss even in warmth.

A superconductor is like a city where electrons stop jostling and start moving in pairs, like people strolling arm in arm. In neodymium-strontium nickelate (Nd₀.₈Sr₀.₂NiO₂), this 'parade' kicks in at around 10 kelvin (minus 263 degrees Celsius), but not uniformly.

An ordinary wire at high frequencies is like a road full of potholes: the signal jumps, and some energy is lost as heat. A superconducting chain made of aluminum and indium arsenide (a semiconductor) turned out to be a smooth highway for microwaves.

Empty space is never truly still. It teems with tiny energy fluctuations, like a sculptor's raw clay. In a new experiment, a thin film of superconducting material was placed inside a cavity designed to trap terahertz light, a form of invisible radiation. The cavity acted as a mold, shaping the vacuum fluctuations around the film.

Ordinary wires: electrons jostle, lose energy, and heat up: that's resistance. In superconductors, some electrons pair up in sync, like dancers swirling without collisions. But these pairs hide: you can't see them directly, only infer their presence from flawless coordination.

Run a current through a contact between a superconductor and a ferromagnet, and you will hear the whisper of the quantum world. In the lab at 0.3 K, that whisper turned into a roar: the shot noise—electrical noise due to the discreteness of charge—was a hundred times louder than theory allows for ordinary contacts.

A magnetic field of 8 tesla is 200 times stronger than Earth's field. Under such a field, superconductivity in a thin film of palladium ditelluride not only survives but persists down to 20 millikelvin, which is a hundred times colder than outer space. For comparison, a thick film of the same material has a critical field 80 times smaller.