Thermodynamic Density of States of Two-Dimensional GaAs Systems near the Apparent Metal-Insulator Transition
Giles AllisonSchool of Physics, University of Exeter, Exeter EX4 4QL, United KingdomE. A. GalaktionovSchool of Physics, University of Exeter, Exeter EX4 4QL, United KingdomA. K. SavchenkoSchool of Physics, University of Exeter, Exeter EX4 4QL, United KingdomС. С. СафоновSchool of Physics, University of Exeter, Exeter EX4 4QL, United KingdomM. M. FoglerDepartment of Physics, University of California San Diego, La Jolla, California 92093, USAM. Y. SimmonsCavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, United KingdomD. A. RitchieCavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, United Kingdom
2006en
ABI
Abstract
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.
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