Phonon and transport measurements in the fractional quantum Hall effect

Abstract

IntroductionThe Coulomb interaction in a twodimensional electron system (2DES) subjected to a quantizing magnetic field leads to the formation of new, fractionally charged quasi-particles at Landau level filling factors p q ν = / (q is an odd-integer) [1][2][3]. This fractional quantum Hall (FQH) effect was very effectively described in the framework of composite fermions (CFs) [4][5][6], new quasi particles with an effective mass m * originating from the Coulomb interaction [7]. In this picture the FQH effect is regarded as an integer quantum Hall effect of these new quasi particles. In particular, at a filling factor 1 2 ν = / these composite fermions can be described as a quasi-free Fermi sea in an effective zero-magnetic field. One of the most important features of the FQH effect are energy gaps ∆. In a simple (noninteracting) CF picture, these gaps originate from the level structure of composite fermions in the form of spin-split Landau levels and can thus be interpreted as either Landau level transitions or spin-excitations. This simple model of CF Landau levels with interaction-dependent cyclotron gap ( B µ ) and Zeeman spin-splitting (µ B) is suitable to describe the main structure of the CF Landau levels.