Friday, 28 August 2015

Don't hold your breath

I dedicate a fair chunk of my book on the way that quantum physics is transforming our world, The Quantum Age, to superconductors. These remarkable substances with no electrical resistance and impressive magnetic properties are already supporting a range applications from MRI scanners to maglev trains, but what is always described as the 'holy grail' of superconductivity is a room temperature superconductor.

The earliest examples had to be cooled within a couple of degrees of absolute zero (-273.15 °C), and even now they need either liquid helium or liquid nitrogen, depending on the type, to keep them cool enough. This is okay for specialist applications, but means they can't break out into everyday everywhere use. But if a superconductor could work easily at room temperature it would transform electronics and electrical products everywhere.

Hence the excitement whenever a new temperature high is announced. This happened recently when the simple compound hydrogen sulfide showed superconducting properties at just 203 K (-70 °C) - okay, not exactly room temperature, but nearly 20 degrees better than the best previous attempt. Immediately, as always with a new announcement, we got claims that room temperature superconductors are on the horizon.

It's possible, but there is a big caveat. Most 'high temperature' superconductors are fancy ceramics featuring the likes of thallium, strontium, copper, oxygen and bismuth. Hydrogen sulfide is suspiciously simple - and there's a reason. Because this was no ordinary H2S. It was compressed using pressures of around 150 gigapascals - that's around 1.5 million times atmospheric pressure. Not surprisingly, achieving this for appliances in the home is probably even less likely than superconductors requiring liquid nitrogen.

I don't want to be negative, though. All such discoveries are highly useful in the slow process of possibly reaching superconducting nirvana. But I wouldn't necessarily expect it any time soon. You can read more on the H2S superconductor here in Physics World.

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