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Author Bogdanovich, S. ♦ Simonian, D. ♦ Kravchenko, S. V. ♦ Sarachik, M. P. ♦ Bhatt, R. N.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ BORON ♦ FERMI LEVEL ♦ SILICON ♦ DOPED MATERIALS ♦ BORON ADDITIONS ♦ ELECTRIC CONDUCTIVITY ♦ TEMPERATURE DEPENDENCE ♦ STRESSES ♦ SCALING ♦ ELECTRON-ELECTRON INTERACTIONS ♦ ENERGY GAP
Abstract Using uniaxial stress to tune the critical density near that of the sample, we have studied in detail the low-temperature conductivity of p-type Si:B in the insulating phase very near the metal-insulator transition. For all values of temperature and stress, the conductivity collapses onto a single universal curve, {sigma}(S,T)=AT{sup 1/2}F[T{sup {asterisk}}(S)/T]. For large values of the argument, the scaling function F[T{sup {asterisk}}(S)/T] is well fit by exp[{minus}(T{sup {asterisk}}/T){sup 1/2}], the exponentially activated form associated with variable-range hopping when electron-electron interactions cause a soft Coulomb gap in the density of states at the Fermi energy. The temperature dependence of the prefactor, corresponding to the T dependence of the critical curve, has been determined reliably for this system, and is {proportional_to}T{sup 0.5}. We show explicitly that neglecting the prefactor leads to substantial errors in the determination of the T{sup {asterisk}}{close_quote}s and the critical exponents derived from them. The conductivity is not consistent with Mott variable-range hopping, exp[{minus}(T{sup {asterisk}}/T){sup 1/4}], in the critical region, nor does it obey this form for any range of the parameters. Instead, the conductivity of Si:B is well fit by {sigma}=AT{sup 1/2}&hthinsp;exp[{minus}(T{sup {asterisk}}/T){sup {alpha}}] for smaller argument of the scaling function, with {alpha}=0.31 related to the critical exponents of the system at the metal-insulator transition. {copyright} {ital 1999} {ital The American Physical Society}
ISSN 01631829
Educational Use Research
Learning Resource Type Article
Publisher Date 1999-07-01
Publisher Place United States
Journal Physical Review, B: Condensed Matter
Volume Number 60
Issue Number 4


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