雅思阅读 88: The Mirage of a Room-Temperature Superconductor（室温超导体的海市蜃楼）

改编自 Nature / Yale Scientific Magazine（2024年2月）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.yalescientific.org/2024/02/room-temperature-superconductors-not-so-fast/

Reading Passage

A. In late July 2023, two preprints appeared on arXiv claiming that a speckle of grey crystalline material, named LK-99, conducted electricity with zero resistance at room temperature and ordinary atmospheric pressure. If true, the discovery would have been one of the most important in the history of physics: lossless power grids, cheap magnetic levitation, quantum computing without refrigeration. The videos posted alongside the papers showed a sliver of the material perched on a magnet, one corner lifted off, wobbling in what looked like the famous Meissner levitation of superconductors. Within days the claim had broken out of specialist journals. Hashtags trended, amateur chemists ordered supplies, hedge funds took positions, and laboratories from Albany to Beijing to Delhi dropped what they were doing to make the stuff. Rarely has a scientific claim travelled from a Korean start-up to the front pages of the world's newspapers in under a week. Rarely, too, has it been dismantled as quickly. By the following December, the official Korean verification committee would conclude that no such superconductor existed. The arc from viral triumph to quiet retraction in five months is, by the standards of academic science, astonishingly fast.

B. Superconductivity is not a small effect. A material becomes superconducting only below a critical temperature, at which electrons pair up and move through the lattice without scattering. The first known superconductors required temperatures within a few degrees of absolute zero, cooled by liquid helium. Later "high-temperature" cuprates, discovered in 1986, work with cheaper liquid nitrogen, but still need to be chilled to minus one hundred and ninety-six degrees. A material that does this in a warm room would violate no known law of physics, but decades of searching had not produced one. A plausible room-temperature candidate therefore attracts the attention that a plausible cure for cancer would attract. Two signatures are considered decisive. The first is exactly zero electrical resistance below the critical temperature. The second is the Meissner effect: the material actively expels internal magnetic fields, which is what makes a superconductor hover above a magnet. Without both, physicists are usually unwilling to believe the claim, however dramatic the video that accompanies it.

C. As teams attempted to reproduce LK-99, the anomalies began to dissolve. Researchers found that the samples in the original preprints contained a common impurity, copper(I) sulphide, or Cu2S. Cu2S is an unremarkable semiconductor, but it undergoes a structural phase transition at around one hundred and ten degrees Celsius — conveniently near the temperature range at which LK-99's reported resistance seemed to collapse. The transition produces a sharp drop in resistivity that looks, on a sloppy plot, exactly like the onset of superconductivity. When Chinese Academy of Sciences researchers and others made LK-99 samples carefully purified to exclude Cu2S, the resistivity drop vanished; the material behaved as a high-resistance insulator. The hovering videos did not fare better either. A true superconductor levitates with its whole base parallel to the magnet, defying gravity from every point. In the LK-99 clips, one corner of the speck stayed glued to the surface, the wobble of a ferromagnet pulled toward metal, not the balanced float of a Meissner expulsion.

D. A small cast of scientists carried much of the debunking in public. Leslie Schoop, a solid-state chemist at Princeton, used X-ray diffraction to show that the reported crystal structure of LK-99 was inconsistent with the claims being made about it, and argued on social media that the dramatic levitation was more likely ordinary magnetism from copper impurities. Her posts, and those of a handful of other physicists, became a kind of crowdsourced peer review — a laboratory floor, in public, in real time. The Korean Society of Superconductivity and Cryogenics convened an official verification committee; its verdict, delivered in December 2023, was blunt. No evidence that LK-99 was a room-temperature, ambient-pressure superconductor had survived replication. The original team's lead authors, some of whom had publicly disagreed with each other during the summer, were left explaining that their samples had been hard to make and easy to misread. A paper in the journal Matter, from Luo Jianlin's group, gave the now-standard account: the resistivity anomaly was Cu2S, not superconductivity.

E. The affair is remembered less for being wrong than for how openly it was wrong. Most failed claims in physics fade quietly, revised or retracted in obscure journals. LK-99 failed in plain sight, on Twitter and Reddit, with live-streamed syntheses and instant X-ray spectra. Physicists who lived through the episode describe it as both a cautionary tale and an unexpected advertisement for their method. Replication, the supposedly plodding boring part of science, did what it was supposed to do, faster than it ever has. The search for a true room-temperature superconductor continues, increasingly in hydrogen-rich compounds that require crushing pressures in a diamond anvil. Whether one will ever be found at ordinary pressure is genuinely unknown. Some theorists argue that the physics of conventional superconductors sets an upper ceiling below room temperature; others point to cuprates as evidence that unconventional mechanisms can break that ceiling. What is certain is that the next time a grey speck of crystal wobbles above a magnet, the world will know not to believe the wobble until at least two independent labs have measured both the zero resistance and the Meissner effect. LK-99 gave physicists a mirage, and it gave the rest of us a view, up close, of the machinery that tells mirages from mountains. It also, in its own strange way, galvanised a generation of solid-state chemists. Applications to study materials chemistry rose; undergraduates who had never touched a furnace volunteered in labs over the summer; and a field that had been quietly shrinking for two decades found itself, for one season, the most famous subject in science.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. What a genuine superconductor must show ii. The viral summer of LK-99 iii. How replication dissolved the anomalies iv. Who led the public debunking v. What the episode teaches science vi. The history of liquid-helium refrigeration vii. Why copper is a good electrical conductor

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. What two signatures are considered decisive evidence of superconductivity? A. High resistance and attraction to magnets. B. Zero electrical resistance and the Meissner effect. C. A grey colour and a crystalline shape. D. Levitation below one hundred degrees and ferromagnetism.

6. What did purified LK-99 samples (without Cu2S) show? A. Perfect zero resistance at room temperature. B. A sharper resistivity drop at one hundred and ten degrees. C. High resistance typical of an insulator. D. Stronger magnetic levitation than the original samples.

7. Why did the LK-99 levitation videos fail to convince physicists? A. One corner of the material remained in contact with the magnet. B. The videos were filmed in slow motion. C. The material was too small to weigh anything. D. The magnet was not powered by electricity.

8. According to the writer, what is the main lesson of the LK-99 affair? A. Social media should be banned from science. B. Replication worked unusually quickly and in public. C. Korean researchers are unreliable. D. Room-temperature superconductors do not exist at all.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. LK-99 was first announced by a research team at a university in Seoul.
10. High-temperature cuprate superconductors still need cooling to around minus one hundred and ninety-six degrees.
11. Cu2S undergoes a phase transition near one hundred and ten degrees Celsius.
12. Leslie Schoop confirmed the LK-99 claims using X-ray diffraction.
13. The search for room-temperature superconductors has now been abandoned.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

The reported resistance drop in LK-99 was caused by a phase transition in the impurity copper(I) (14) __________, and the apparent levitation was ordinary (15) __________ from copper impurities.

答案与解析

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