Fractional quantum Hall effect without energy gap

Abstract

In the fractional quantum Hall effect regime we measure diagonal (${\rho }_{xx}$) and Hall (${\rho }_{xy}$) magnetoresistivity tensor components of two-dimensional electron system (2DES) in gated GaAs/Al${}_x$Ga${}_{1-x}$As heterojunctions, together with capacitance between 2DES and the gate. We observe 1/3- and 2/3-fractional quantum Hall effect at rather low magnetic fields where corresponding fractional minima in the thermodynamical density of states have already disappeared manifesting complete suppression of the quasiparticle energy gaps.

4 pages, 4 figures