Department of Physics, Ben-Gurion University, Beer
Sheva 84105, Israel
(Received 27 December 1999)
Recently, a simple noninteracting-electron model, combining local
quantum tunneling via quantum point contacts and global classical
percolation, has been introduced in order to describe the observed
"metal-insulator transition" in two dimensions [Y. Meir,
Phys. Rev. Lett. 83, 3506 (1999)]. Here, based upon that model,
a two-species percolation scaling theory is introduced and compared to
the experimental data. The two species in this model are, on one hand,
the "metallic" point contacts, whose critical energy lies
below the Fermi energy, and on the other hand, the insulating quantum
point contacts. It is shown that many features of the experiments, such
as the exponential dependence of the resistance on temperature on the
metallic side, the linear dependence of the exponent on density, the
e2/h scale of the critical resistance,
the quenching of the metallic phase by a parallel magnetic field and
the nonmonotonic dependence of the critical density on a perpendicular
magnetic field, can be naturally explained by the model. Moreover,
details such as the nonmonotonic dependence of the resistance on
temperature or the inflection point of the resistance vs the parallel
magnetic field are also a natural consequence of the theory. The calculated
parallel field dependence of the critical density agrees excellently with
experiments, and is used to deduce an experimental value of the
confining energy in the vertical direction. It is also shown that the
resistance on the metallic side can decrease with decreasing
temperature by an arbitrary factor in the nondegenerate regime (T<~EF).
©2000 The American Physical Society
PACS: 71.30.+h, 73.40.Qv, 73.50.Jt
Full Text:
References
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