The origin of fractional quantum Hall effect (FQHE) at 4/11 and 5/13 has remained controversial. We make a compelling case that FQHE is possible here for fully spin polarized composite fermions, but with an unconventional underlying physics. Thanks to a rather unusual interaction between composite fermions, FQHE here results from the suppression of pairs with relative angular momentum { \em three} rather than one, confirming the exotic mechanism proposed by W\'ojs, Yi and Quinn [Phys. Rev. B { \bf 69}, 205322 (2004)]. We predict that the 4/11 state reported a decade ago by Pan { \em et al.} [Phys. Rev. Lett. { \bf 90}, 016801 (2003)] is a conventional partially spin polarized FQHE of composite fermions, and estimate the Zeeman energy where a phase transition into the unconventional fully spin polarized state will occur.
Categories: cond-mat.mes-hall