THE THERMODYNAMICS OF A CHARGED FERMION LAYER AT HIGH R(S) VALUES

We report the measurement of the chemical potential of a two-dimension al hole layer in wide temperature and density ranges. Due to their hea vy mass, the holes are in a regime where the ratio of Coulomb to Fermi energies r(s) is very high, thus facilitating the first detailed stud y of the full temperature-dependent crossover from the strongly intera cting degenerate regime to the classical ideal gas limit. The measured low-temperature chemical potential and inverse compressibility are ne gative and uninfluenced by temperature. At T approximate to 17 K they simultaneously and abruptly become temperature-dependent for all carri er concentrations. As the temperature is further raised, the inverse c ompressibility becomes less negative and reverses sign. An ideal class ical gas behavior is attained only at temperatures of the order of the interaction energy, more than an order of magnitude larger than the F ermi energy.