Level 1 — Absolute Beginner
Electricity moves through wires. But the wires get warm, and some energy is lost.
A superconductor is a special material. Electricity moves through it and no energy is lost. But today it only works when it is very, very cold.
Scientists in Europe looked at one of these materials with a strong microscope. They saw that tiny electrons join in pairs. These pairs are strong.
The scientists say the pairs can live at room temperature. This is good news. But the pairs must also move together. That is the next problem to solve.
- electricity
- The power that makes lamps, phones and machines work.
- wires
- Long, thin pieces of metal that carry electricity.
- energy
- Power that makes things move, shine or get warm.
- material
- What a thing is made of, like metal, wood or glass.
- cold
- Not warm. Ice is like this.
- electrons
- Very, very small things that carry electricity.
- pairs
- Groups of two.
- room temperature
- How warm it is in a normal room, about 20 degrees.
Level 2 — Elementary
Superconductors are materials that carry electricity with no resistance, so no energy is wasted as heat. Hospitals already use them in MRI scanners. The problem is that they only work at extremely low temperatures, which makes them expensive to use.
For forty years, scientists have dreamed of a superconductor that works at room temperature. A new study in the journal Science, by researchers from Utrecht, Leiden and Munich, explains one part of the puzzle.
For superconductivity, two things must happen. First, electrons have to join together in pairs. Second, all the pairs have to move in step, like dancers. The team studied a material that contains copper and measured tiny changes, called noise, in an electric current.
The noise showed that the pairs are held together very strongly. According to the researchers, the pairs could survive up to room temperature. What is missing is the second condition. The scientists did not make a room temperature superconductor, but they now know better where to look.
- resistance
- The way a material slows down electricity and turns some of it into heat.
- wasted
- Used badly or lost without any benefit.
- scanners
- Machines that take pictures of the inside of the body.
- journal
- A magazine where scientists publish their research.
- puzzle
- A problem that is difficult to understand or solve.
- in step
- Moving together at the same time and in the same way.
- current
- A flow of electricity.
- condition
- Something that must be true before another thing can happen.
Level 3 — Intermediate
A superconductor that works at room temperature would transform power grids, medical scanners and computing, because such materials conduct electricity without any resistance. Today's best examples must still be cooled far below freezing. A study published in Science by physicists from Utrecht University, Leiden University and LMU Munich now clarifies which obstacle actually stands in the way.
Superconductivity needs two ingredients. Electrons, which normally repel one another, must bind into pairs, and those pairs must then become coherent, meaning that they all move in a synchronized way. The team, whose paper lists Jiasen Niu as first author, examined a copper-based crystal known as BSCCO, one of the cuprates discovered in the 1980s.
Using a scanning tunnelling microscope, the researchers sent a current from an atomically sharp needle into the crystal and recorded its noise, the tiny random fluctuations in the flow. The size of that noise reveals whether charge arrives one electron at a time or two at a time. Pairs appeared at much higher energies than expected, matching a mysterious feature of cuprates called the pseudogap, and a magnetic field made them disappear again.
The binding energy they measured, up to about 70 millielectronvolts, is large enough for pairs to persist at room temperature, the authors say. Pairing, in other words, is not the bottleneck; coherence is. The team stresses that it has not produced a room temperature superconductor. The record at normal pressure remains 151 kelvin, about minus 122 degrees Celsius, set in March by a group in Houston. But the search has become narrower.
- conduct
- To allow electricity or heat to pass through.
- obstacle
- Something that blocks progress.
- repel
- To push away.
- coherent
- Here: all acting together as one.
- fluctuations
- Small, irregular changes up and down.
- pseudogap
- A range of energies in some superconductors where few electron states are available, even above the superconducting temperature.
- bottleneck
- The one point that slows down or limits a whole process.
- persist
- To continue to exist.
Level 4 — Advanced
For four decades the cuprates, copper oxide ceramics that superconduct at temperatures unexplained by conventional theory, have confronted physicists with a riddle: what is the pseudogap, the strange depletion of electronic states that appears well above the temperature at which resistance vanishes? An experiment reported in Science by a collaboration from Utrecht, Leiden and Munich offers one of the most direct answers yet, and with it a sharper view of what separates existing materials from superconductivity at room temperature.
The physicists exploited shot noise, the granular hiss produced because electric current is carried by discrete charges. When a current tunnels from the tip of a scanning tunnelling microscope into a sample, the magnitude of that noise betrays the size of each charge packet; a doubling signals that electrons are crossing two at a time. Mapping the noise across a crystal of the cuprate BSCCO, the team found paired carriers at energies that track the local pseudogap, reaching about 70 millielectronvolts, and saw the signal collapse toward single-electron values in a magnetic field.
The implication is that the pseudogap is, at least in large part, a pairing gap, and that pairs form far more robustly than the modest transition temperatures of cuprates would suggest. On the authors' reckoning the pairing is strong enough to endure at room temperature. What fails is phase coherence, the collective locking of all pairs into a single quantum state, without which paired electrons still dissipate energy. The bottleneck, in short, is not glue but order.
Caution is warranted on two fronts. The paper, which circulated as a preprint in 2024, concedes that the pseudogap may reflect competing forms of local order as well as pairing, and the pairing energy varies markedly from one nanometre-scale patch to the next. Nor does anything in it constitute a room temperature superconductor; the ambient-pressure record still stands at 151 kelvin. But by indicating that coherence, not pairing, is the property to engineer, the work gives materials scientists a more precise target than they have had before.
- riddle
- A mystery that is hard to explain.
- exploited
- Made good use of something.
- discrete
- Separate and individual, not continuous.
- magnitude
- Size or strength.
- robustly
- In a strong way that does not easily break.
- dissipate
- To lose energy, usually as heat.
- warranted
- Justified by the circumstances.
- preprint
- A scientific paper shared publicly before formal review and publication.
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