Is there any other superfluid element except helium? Everywhere we see and speak about superfluidity, we just speak about superfluid helium. but is't there any other element or material or system which acts as a superfluid?
Yes, para hydrogen, in a limited manner.
Recent work at Göttingen has revealed convincing evidence for superfluidity in liquid hydrogen, the only liquid other than helium to exhibit this quantum behaviour.
From a spectroscopic experiment on droplets of parahydrogen, it has been discovered that properties of superfluid are observed in a system of about 14 to 16 parahydrogen molecules.
It should be emphasized that superfluidity in a shell containing about 15 hydrogen molecules does not necessarily mean that the phenomenon will ever be observed in bulk liquid. Indeed, it probably will not, due to the difficulty of maintaining the liquid state at low enough temperatures. But the results for droplets seem to have given us a new superfluid, presumably quite different from the liquid heliums with which low-temperature physicists are so familiar. It will be an interesting challenge to find ways of studying superfluid parahydrogen in order to establish its properties.
I am puzzled by the
"difficulty of maintaining the liquid state at low enough temperatures".
I worked for years with data from the 2m hydrogen bubble chamber, lots of liquid hydrogen there.