Longitudinal conductivity in Si/SiGe heterostructure at integer filling factors

Abstract

We have investigated temperature dependence of the longitudinal conductivity ${\sigma }_{xx}$ at integer filling factors $\nu =i$ for Si/SiGe heterostructure in the quantum Hall effect regime. It is shown that for odd $i$, when the Fermi level $E_F$ is situated between the valley-split levels, $\Delta {\sigma }_{xx}$ is determined by quantum corrections to conductivity caused by the electron-electron interaction: $\Delta {\sigma }_{xx}(T)\sim \ln T$. For even $i$, when $E_F$ is located between cyclotron-split levels or spin-split levels, ${\sigma }_{xx}\sim \exp [-{\Delta }_i/T]$ for $i=6,10,12$ and $\sim \exp [-(T_{0i}/T){]}^{1/2}$ for $i=4,8$. For further decrease of $T$, all dependences ${\sigma }_{xx}(T)$ tend to almost temperature-independent residual conductivity ${\sigma }_i(0)$. A possible mechanism for ${\sigma }_i(0)$ is discussed.

6 pages, 8 figures (included), accepted in Phys. Rev. B