Existence of Fractional States Even in 3D?

It is always fun when you read about new and unexpected observations, even if it is just an initial observation that requires much more studies.

We all know about fractional quantum hall/fractional charge phenomenon observed and verified many years ago. These were seen on 2D material where the behavior observed appears to indicate that the charge carriers have fractional charges (e/3 at that time). The understanding that we have today is that the dimensionality (i.e. 2D) is the requirement for such an effect to take place.

Now we have preliminary indication that this may not be the case. A report in this week's Science on Bismuth indicates hints that such fractional effects can also be seen in 3D material (K. Behnia et al., Science v.317, p.1729 (2007)). While the signal may not be as clean as the 2D case, there are distinct indications that some form of fractionalization (they have assigned a filling level as 1/2) is taking place.

So now, if this is true, we will have to go back and revise our understanding of the behavior of strongly-correlated electrons and the role of dimensionality in such a system.

Zz.