What is jellium aromaticity?

As I understand, if a molecule is cyclic and planar, then every atom in the ring must be $\ce{sp^2}$-hybridized and the molecule must have [4n+2] π electrons, where n∈N (Hückel’s rule).


An [article](https://www.chemistryworld.com/news/new-rule-predicts-stabilising-aromaticity-in-open-shell-metal-clusters/3010515.article) in Chemistry World by Sam Howell ("New rule predicts stabilising aromaticity in open-shell metal clusters", 21 MAY 2019), talks about jellium aromaticity.


[![enter image description here](https://i.stack.imgur.com/j23iw.png)](https://i.stack.imgur.com/j23iw.png)


image source : <https://www.chemistryworld.com/news/new-rule-predicts-stabilising-aromaticity-in-open-shell-metal-clusters/3010515.article>


My question is what is jellium aromaticity? 


Does it have anything to do with Hückel's rule?


