You may have heard of superfluids and superconductors, so why not supersolids? In 2004 Moses Chan and Eunseong Kim thought they had discovered that super-cooled helium ice could essentially walk through walls – a defining characteristic of a supersolid.
The experiment was to make a cylinder with tiny nanopores in its walls, fill the pores with solid helium ice, suspend the cylinder from a torsional spring, and then give it a little twist. Like a kid on a swing set, the cylinder started rotating back and forth, with a frequency depending on its mass. As they supercooled the cylinder even further, they saw that the oscillation frequency changed, as if it had less mass!
The interpretation was that the helium had become a supersolid – it had begun moving through the walls of the cylinder, and thus did not contribute to its rotational inertia.
This girl's spinning period of oscillation depends on her mass. And possibly temperature. (DavidMaisel via wikimedia.org)
Although Chan was cautious about his interpretation, even titling the paper “Probable observation of a supersolid helium phase”, it still set the physics world supersolidly abuzz. Other groups seemed to confirm the findings, but strangely, different groups were measuring different magnitude effects. Finally, based on a suggestion from another group, Chan went back and did his experiment slightly differently. The worry was that larger helium crystals could be elastic, and since this elasticity would change with temperature, it could also alter oscillation frequency as temperature decreased. So Chan eliminated all spaces for larger, elastic helium crystals in the cylinder and found that … the supersolid effect disappeared.
After playing a sad trombone, Chan dutifully reported his result in a new paper, and science progressed. This is how science works: you report results and interpretations, and then other groups do their best to make sure everything makes sense. Normally, mistakes are caught early on by self-skepticism and peer review, but sometimes an honest misinterpretation can get through. When it’s caught, most scientists would respond magnanimously the way Chan did: “I’m in an awkward position, since we started the whole damn thing, but I’m glad we were the ones who found the explanation.”
So when the headlines blare about rare instances of fraud, remember the legions of honest scientists constantly working to learn how the world really works, whose integrity doesn’t always get the respect and attention it deserves.
Absence of supersolidity in solid helium in porous vycor glass
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