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تسجيل مستخدم جديدSuppression of metallic behavior in two dimensions by spin flip scattering
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We study the effect of the disorder on the metallic behavior of a two-dimensional electron system in silicon. The temperature dependence of conductivity $sigma (T)$ was measured for different values of substrate bias, which changes both potential scattering and the concentration of disorder-induced local magnetic moments. We find that the latter has a much more profound effect on $dsigma/dT$. In fact, the data suggest that in the limit of $Tto 0$ the metallic behavior, as characterized by $dsigma/dT < 0$, is suppressed by an arbitrarily small amount of spin flip scattering by local magnetic moments.
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Magnetoconductance (MC) in a parallel magnetic field B has been measured in a two-dimensional electron system in Si, in the regime where the conductivity decreases as sigma (n_s,T,B=0)=sigma (n_s,T=0) + A(n_s)T^2 (n_s -- carrier density) to a non-zer
o value as temperature T->0. Very near the B=0 metal-insulator transition, there is a large initial drop in sigma with increasing B, followed by a much weaker sigma (B). At higher n_s, the initial drop of MC is less pronounced.
Experiments on a sufficiently disordered two-dimensional (2D) electron system in silicon reveal a new and unexpected kind of metallic behavior, where the conductivity decreases as sigma (n_s,T)=sigma (n_s,T=0)+A(n_s)T^2 (n_s-carrier density) to a non
-zero value as temperature T->0. In 2D, the existence of a metal with dsigma/dT>0 is very surprising. In addition, a novel type of a metal-insulator transition obtains, which is unlike any known quantum phase transition in 2D.
The temperature dependence of conductivity $sigma (T)$ in the metallic phase of a two-dimensional electron system in silicon has been studied for different concentrations of local magnetic moments. The local moments have been induced by disorder, and
their number was varied using substrate bias. The data suggest that in the limit of $Tto 0$ the metallic behavior, as characterized by $dsigma/dT < 0$, is suppressed by an arbitrarily small amount of scattering by local magnetic moments.
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