Systematic study of thermal transport of composite fermions around filling factorsν=1±12m

Abstract

The thermopower is calculated for a two-dimensional electron and hole gas at low temperatures in the fractional quantum Hall-effect regime around filling factors $\ensuremath{\nu}=1\ifmmode\pm\else\textpm\fi{}\frac{1}{2m},$ $2m$ being the number of flux quanta attached to each carrier in the composite fermion (CF) picture. The general expressions obtained are applied to the $2m=2$ (i.e., $\ensuremath{\nu}=\frac{1}{2}$ and $\ensuremath{\nu}=\frac{3}{2})$ and $2m=4$ (i.e., $\ensuremath{\nu}=\frac{3}{4}$ and $\ensuremath{\nu}=\frac{5}{4})$ cases. The analysis leads to the determination, on a firm theoretical base, of the actual number of carriers involved in the expression of the thermopower of the system. We demonstrate the significance of the contribution of the nondiagonal component of the composite fermion thermopower to the diagonal component of the total thermopower of the system around $\ensuremath{\nu}=\frac{3}{2}.$ We investigate the dependence of the CF's effective mass on the magnetic field analyzing the ratios ${S}_{xx,\ensuremath{\nu}=3/2}{/S}_{xx,\ensuremath{\nu}=1/2}$ and ${S}_{xx,\ensuremath{\nu}=3/4}{/S}_{xx,\ensuremath{\nu}=1/2},$ together with the available experimental data, for the diffusion case. We also analyze the phonon-drag case. Our theoretical results are in agreement with the experimental data.