We report on the electrical conductivity σ of a series of nominally uncompensated neutron-transmutation-doped isotopically enriched 70Ge:Ga samples with the Ga concentration [Ga] near Nc for the metal-insulator transition. σ of all insulating samples obeys lnσα−(T0/T)½ with T0α(Nc − [Ga])/Nc while the zero temperature conductivity σ(0)of the metallic samples is T0α(([Ga] −Nc)/Nc))ν with the critical exponent ν ≈ 5. The values of Nc obtained from the two independent scalings of T0 and σ(0) are identical, i.e., ½ ≈ 5 is established unambiguously for uncompensated Ge:Ga.
|ジャーナル||Physical review letters|
|出版ステータス||Published - 1996|
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