Surprise observation of negative mass in exciton polaritons

A surprise observation of negative mass in exciton-polaritons has added yet another dimension of weirdness to these strange light-matter hybrid particles.

Dr Matthias Wurdack, Dr Tinghe Yun and Dr Eliezer Estrecho from the Department of Quantum Sciences and Technology (QST) were experimenting with exciton polaritons when they realised that under certain conditions the dispersion became inverted – equating to a negative mass.

To add to the surprise, the unexpected cause has turned out to be losses.

“We did not expect that – the dispersion followed very unconventional behaviour,” said Dr Wurdack, who is a member of the FLEET as well as QST.