quasiparticle

A laser pulse slams into a gas cloud and knocks electrons out of it, leaving behind a bubble: a cavity almost devoid of particles. This bubble races through the plasma at nearly the speed of light, and its walls drag along the electrons trapped inside, much like a speedboat tows a water skier.

A stone drops into a pond, and ripples spread across the water. In the same way, massive bodies generate gravitational waves, except it's space itself that ripples. So far, these waves have been caught by giant detectors that barely flinch as a wave passes through. But what happens on the microscopic scale, inside a tiny piece of matter?

In the quantum world, particles sometimes behave like acrobats on invisible tightropes. An instanton field is a brief vortex that appears and vanishes in an instant. When a fermion (a particle like an electron) enters such a vortex, its energy does not stay put. Instead, it smoothly slides from one level to another, like a ball rolling down a hill.

In the world of quantum particles, there are introverts — anyons. They are unlike familiar electrons or protons. If you swap two such introverts, they remember the maneuver, as if leaving an invisible trace.

In a crystal, heat travels on waves. Atoms vibrate, and these vibrations, called phonons, carry energy from the hot edge to the cold one. For a long time, it was believed that if phonons hit resonance (their frequencies exactly match) and can exchange energy, heat would flow like an avalanche. It turns out that's not the case.

A superconducting qubit is like a finicky musical instrument: until you tune it, you won't get a clean note. But even after tuning, the pitch drifts. The culprits are tiny defects in the material that physicists call two-level systems. They're like invisible cracks that appear and disappear, throwing off the processor's rhythm.

At low temperatures, many materials become superconductors — current flows without resistance. But how exactly does this happen if electrons were initially trapped in an insulator? Half a century ago, Philip Anderson suggested that the answer lies in a special quantum dance of particles.

An empty resonator isn't truly empty. Even in an absolute vacuum, where not a single photon exists, quantum fluctuations persist. They resemble ripples on water in a dead calm: the surface appears smooth, but molecules keep jittering. Physicists have learned to turn this jitter into real waves.

The quantum world is tricky: sometimes particles confined to a flat layer and pierced by a strong magnetic field start behaving like a liquid made not of whole electrons but of their fractions — fractional charges. This is the fractional quantum Hall effect.

Graphene, a sheet of carbon one atom thick, behaves like a calm water surface, until superconductivity appears. Then, unusual waves ripple across it, like the circles from a thrown stone: pairs of electrons move without friction.

After a hit, a black hole rings like a bell. But instead of sound, it emits gravitational waves whose frequency rapidly decays: these are called quasinormal modes. From such a 'ring,' you can infer the hole's mass, spin, and other properties.

A massive aluminum cylinder weighing a ton hangs in a vacuum. A gravitational wave, a ripple in spacetime, passes through it, and the bar begins to tremble almost imperceptibly. That trembling can be heard as sound: gravitational waves turn into a phonon — a quantum of sound vibrations.

A mosaic of squares and triangles covers the floor without gaps, yet it never settles into a simple repeating pattern. Such a pattern is a quasicrystal — a solid where atoms are arranged not periodically but according to a pattern of several waves of different lengths. These waves are incommensurate with each other, and together they create long-range order.

In the city of elementary particles, there is a house right on the edge — X(3872). It sits exactly on the line separating it from decaying into two lighter structures: a D meson and an anti-D meson. Give it a nudge, and it would fall apart. But the house stands. Physicists have long debated what holds it together.

In 1984, the world of crystallography was turned upside down: sharp diffraction peaks with fivefold symmetry were discovered in an alloy of aluminum and manganese – as if nature had mocked the strict theorems forbidding repeating patterns from having axes of order 5, 8, 10, or 12.

In the world of two-dimensional materials, states sometimes emerge that are as extraordinary as they are fragile. One of them — the fractional anomalous Hall crystal (FAHC)—is like a quantum centaur: half ordered lattice, half topological liquid.

Ever since Fritz Zwicky noticed that galaxy clusters were moving too fast, and Vera Rubin measured the rotation of spiral arms, dark matter has remained cosmology's greatest mystery.

Quantum tunneling — the ability of particles to pass through barriers forbidden by classical physics — powers stars with thermonuclear fusion, ignites primordial nucleosynthesis, and gives us flash memory.

Quantum matter rarely treats us to the spectacle of self-motion. Where the classical world teems with starling murmurations, fish schools, and bustling bacteria, quantum thermodynamics long remained serene.

A black hole is not a dead object. After a disturbance, such as merging with another hole, it rings like a bell. This ring is not just a sound but a complex set of damped oscillations called quasinormal modes. Their frequency and damping rate depend on the hole itself: its mass, charge, and spin.

Imagine a skyscraper assembled not from individual bricks but from entire studio apartments. That's exactly how the Au₆Te₁₂Se₈ crystal is built: its nodes are not atoms but superatomic clusters of gold and chalcogens that behave as single quantum objects.

In boiling water you can see a prototype of a quantum trick: if part of the liquid turns into long-lived vapor bubbles, the main mass cools down. This is exactly what happens when you sharply jolt a system of interacting electrons: doublons flare up — pairs of particles that absorb excess energy and don’t decay for an astonishingly long time.

A pebble falls into a pond, and ripples spread across the water. In the quantum world, the pond is not made of water but of many identical particles, and the pebble is also a particle, just a foreign one. Such a foreign particle is called a Fermi polaron.

In a long corridor, a crowd of people tries to keep as far apart as possible. In a spacious hall, they would simply spread out, but here the walls squeeze them so tightly that they have to move single file, coordinating every step. Electrons in graphene layers twisted by a tiny angle behave in a similar way.

You're looking for a quiet room for an important conversation. You step into a space, and hear silence. But upon closer inspection, you find that in one corner the ventilation is simply broken, and in another there's a hole in the floor that absorbs sound.

In the microcosm, long-range forces, gravity or electricity, do not switch off even at enormous distances. Therefore, any particle drags behind it a trail of soft (i.e., very low-energy) photons or gravitons. This trail is called the "dress"; without it, calculations fall apart and infinities appear.

A billiard game would be strange if the balls had no mass. They wouldn't collide but would pass through each other, ignoring obstacles. That's roughly what it looks like to imagine light as a stream of classical particles — tiny elastic bodies flying in straight lines. A new proof puts an end to that picture.

The universe is like a layered cake, and our layer (stars, planets, and people) is just one of many. In a neighboring layer, which physicists call the hidden sector, processes are boiling away. This work describes one such process: a first-order phase transition, where matter abruptly changes state, like water turning into ice.

A cloud of rubidium atoms falls into a trap made of light. Lasers and magnetic fields arrange it like a crystal lattice, but the cells here are not fractions of a millimeter: they are fractions of a micrometer.

A supersolid is matter that is both crystalline and fluid. It is created from atoms cooled almost to absolute zero. In new work, physicists obtained such a substance as a triangular lattice of droplets. Each droplet oscillates in its own rhythm.

A lump of dark matter drifts through the void — invisible, almost intangible. No one knows what it's made of, but a new study suggests viewing it as a drop of quantum liquid. Two kinds of fermion particles — call them "heavy" (ψ) and "light" (χ)—exchange signals via a third mediator particle (φ), like floats tied to a single line.

A stone falls into a pond, and ripples spread across the water. Long waves and short ones travel at the same speed: that's how ordinary sound behaves in almost any medium. But in quantum liquids, things can be different. Physicists considered a superfluid where particles move along a "flat" energy band.

Imagine an orchestra where every musician plays their own part without listening to the others. Suddenly, without any visible command, neighboring musicians begin to sync perfectly, yet there is still no overall melody.

Two quantum particles are linked by an invisible thread: one loses energy, the other gains it, but the total remains unchanged. If you watch only the first, its oscillations don't fade — the rhythm is steady, like that of a cosmic pulsar, even though it seems that entropy and chaos are increasing.

Drop a pebble into a pond, and ripples spread across the water. Strike a bell, and it rings at its own frequency. When a black hole collides with another, it too 'rings'—except instead of sound, it's the trembling of space itself.

Sound travels through a medium at a certain speed. If the medium moves faster, the sound gets swept along by the flow — like a wood chip pulled into a whirlpool. In superfluid helium — a frictionless liquid — rapid rotation spawns vortex funnels. Inside them, an acoustic black hole forms: a region from which sound cannot return.

The pendulum of an old clock swings because a spring mechanism gives it a regular nudge. Now imagine a pendulum that decides on its own when to swing, and does so with a steady rhythm, just because the room is warm and there's a slight draft. That's exactly how time crystals behave, born in clumps of light and matter inside a semiconductor chip.

Tile a floor with identical triangles, and you get a boring repeating pattern. But what if you want the pattern to never repeat, yet use just one tile? For a long time, mathematicians were sure it couldn't be done: you'd need at least two different shapes. The famous Penrose mosaic is a case in point: rhombi with acute and obtuse angles arrange into an infinitely varied but strictly ordered pattern.

In a thin sandwich of semiconductors, light creates pairs, an electron and a positive hole, that stick together like a ball on a rubber band. Normally, such pairs, called excitons, quickly emit light and vanish. But there are others, dark ones, that live hundreds of times longer because their internal structure forbids them from easily giving off energy.

An ordinary battery in a phone stores energy in chemical bonds — slowly, with heat and wear. A quantum capacitor works differently: it charges not with matter but with rhythm. A swing that is pushed in time with its motion accumulates energy in the motion itself, without friction.