Thermodynamic density of states of two-dimensional GaAs systems near the apparent metal-insulator transition.
We perform combined resistivity and compressibility studies of two-dimensional hole and electron systems which show the apparent metal-insulator transition--a crossover in the sign of deltaR/deltaT with changing density. No thermodynamic anomalies have been detected in the crossover region. Instead, despite a tenfold difference in r(s), the compressibility of both electrons and holes is well described by the theory of nonlinear screening of the random potential. We show that the resistivity exhibits a scaling behavior near the percolation threshold found from analysis of the compressibility. Notably, the percolation transition occurs at a much lower density than the crossover.
Allison
G
G
School of Physics, University of Exeter, Exeter EX4 4QL, United Kingdom.
Galaktionov
E A
EA
Savchenko
A K
AK
Safonov
S S
SS
Fogler
M M
MM
Simmons
M Y
MY
Ritchie
D A
DA