The 5/2 engima in FQHE

Some progress in QHE. Despite the toil invested in this startling subject and estoric thoughts and concepts invoked, QHE, in my opinion, is far from being well understood. The simplicity of the phenomena makes strong contrast with the intricacy of theoretical context. This contrast makes me feel uncomfortable with the present understanding. Now here is an experiment that shows the inadequacy. Is the FQHE indeed so different from IQHE ?

larger mystery surrounding the fractional quantum Hall effect in the second Landau level. The other observed fractions, such as 2 + 1/3, 2 + 2/3, 2 + 2/5, 2 + 3/5, match those observed in the lowest Landau level, but detailed calculations show, surprisingly, that the model of weakly interacting composite fermions, which is successful for the explanation of the lowest Landau level fractions, is not adequate for these second Landau level fractions. A resolution of the second Landau level fractional quantum Hall effect is likely to lead to much exciting physics.

PRL 105, 096801 (2010)