Two-dimensional density of states in the extreme quantum limit

We have measured the density of states of a two-dimensional electron gas from the weak-field limit to the extreme quantum limit and obtained quantitative information about the density of states at filling factors of frac13; and frac23;. Our magnetocapacitance measurements were made at magnetic field strengths up to 29 T at temperatures between 0.4 and 4.2 K using modulation-doped GaAs-AlxGa1-xAs heterostructures on conducting substrates. © 1986 The American Physical Society.