A paper posted to arXiv last month claims to have achieved superconductivity at room temperature, but other physicists say the data may be incorrect.
When it comes to applied quantum mechanics, there are two “holy grails” in the field.
One is building a large scale quantum computer and the other is achieving superconductivity above the freezing point of water, colloquially known as room temperature superconductivity. Superconductors are materials that have no electrical resistance—meaning that electrons can flow through the object unimpeded—but so far physicists have only been able to achieve superconductivity by bringing the materials to incredibly cold temperatures. If superconductivity could be harnessed at room temperature, it would allow for the free transport of energy, wildly faster computers, and incredibly precise sensors. Indeed, it would fundamentally change the world.
In July, Dev Thapa and Anshu Pandey, two well-regarded chemical physicists from the Indian Institute of Science in Bangalore, India, posted a paper to arXiv that claims they managed to achieve “superconductivity at ambient temperature and pressure conditions” using a matrix of gold and silver particles. This announcement understandably shocked the physics community. Not only did Thapa and Pandey claim to have achieved room temperature superconductivity, but they did it using gold and silver, which have never demonstrated superconductivity even at extremely cold temperatures.
Yet as the physics community began to look closer at the data, something didn’t seem right. On Friday, Brian Skinner, a postdoctoral physicist at MIT, posted a comment on Thapa and Pandey’s arXiv paper that noted a strange correlation between two independent measurements.
Take a look at the green and blue dots in the above graph. They represent the noise measured during two separate experiments run by Thapa and Pandey to test the magnetic susceptibility of their superconducting material. Noise is by definition random, so there shouldn’t be any correlation between the noise measured in one experiment and the noise measured in another experiment. Yet in the graph above, the blue dots are exactly correlated to the green dots, but shifted down a little.
“If you see two measurements, made at different times and under slightly different conditions, and you get the exact same pattern of random variations, that’s very unusual,” Skinner told me in an email. “It’s not clear yet what this repeated noise means. It could be a real and previous unknown natural phenomenon, or it could be an artifact of the measurement process which we also don’t understand. But it’s a sufficiently strange observation that it’s worth paying attention to.”
Over the weekend, Skinner received a reply to his critique from Thapa and Pandey, he said in a tweet. According to Skinner, the authors said that they hadn’t noticed the correlation before, but didn’t back down from their claim that they had observed superconductivity at room temperature. Nevertheless, this remarkable correlation in the noise data had to be explained.
On Saturday, Pratap Raychaudhuri, a physicist at the Tata Institute of Fundamental Research in Mumbai, made a public Facebook post trying to explain how this data could be legit. One possibility raised by Raychaudhuri is that the noise reported by Thapa and Pandey is not noise at all, but is actually a part of the signal being measured that arises from the movement of particles in a magnetic field. As Raychaudhuri explained, it would be possible to reproduce the noise observed in magnetic fields below a certain strength (that is, below 3 Teslas). Below this strength the particles wouldn’t fully detach from one another and would thus retain a “memory” of their initial formation. Thus if the researchers were to apply a magnetic field of a certain strength, turn it off, and then apply it to the same sample of particles again, they’d expect to see the same noise pattern because the particles would retain their initial starting configuration each time.
Yet as Raychaudhuri pointed out, this possible explanation still doesn’t solve all the issues in the paper, which went beyond curious noise correlations.
The most significant anomaly, in this respect, is that the gold and silver nanostructure exhibited a resistive (in other words, electrical) and magnetic transition to a superconductor at the same temperature. According to Raychaudhuri, this would only happen if the test was done on the same sample, which the authors reported was not the case. Raychaudhuri argued that these issues could be easily resolved if the authors would share their test samples with the wider research community, which he said so far they haven’t done.
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