Three years ago chemist Richard Mandle and colleagues at the University of York in the UK published a surprising observation.1 They’d created a new organic molecule, now known as RM734. Because of its elongated shape and large electric dipole moment, they thought it might be useful in liquid-crystal applications.

Cooling a hot sample of RM734 molecules below 188 °C transformed it, as expected, from an ordinary isotropic liquid into a nematic liquid-crystal phase, characterized by its orientational order without positional order. But as the researchers cooled the liquid further and monitored its heat capacity, they saw the clear signature of a second phase transition, at 133 °C, that they were unable to explain. Above and below the transition temperature, the material looked exactly the same.

Now, in collaboration with Mandle and others, physicists Nerea Sebastián and Alenka Mertelj, both at the Jožef Stefan Institute in Ljubljana, Slovenia, have figured...

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