Effect of in-plane Magnetic Field on Conductivity of Two Dimensional Electrons on Silicon Surface

The two dimensional system of electrons in silicon inversion layers is one of the most interesting low dimensional systems, where the effects of externally controlled electron-electron interactions are observed directly. Among several fascinating phenomena discovered in the past few years, one of the most intriguing and dramatic is the strong effect of in- plane magnetic field on the 2D conductivity. It was found$^a$ that the energy scale associated with this magnetic field response goes to zero at a density $n_0=0.8 \times 10^{11}$ cm$^{-2}$, indicating the approach to a quantum phase transition.\\ In my talk the effects of in-plane magnetic field on the conductivity of two dimensional electron systems in Si-MOSFETs will be discussed. We will report recent experimental results demonstrating that the application of an in-plane magnetic field significantly reduces the metallic ($d\sigma/dT<0$) temperature dependence of the conductivity over a broad range of electron densities, extending deep into the metallic regime, where the high field conductivity is of the order of $10 e^2/h$. The strong suppression (or ``quenching'') of the metallic behavior by the magnetic field indicates that the spin degrees of freedom play an important role in the transport properties of these two-dimensional systems. \\ Work done in collaboration with Yeekin Tsui, M. P. Sarachik and Teun M. Klapwijk.\\ $^a$ S. A. Vitkalov, Hairong Zheng, K. M. Mertes, M. P. Sarachik, T. M. Klapwijk Phys. Rev. Lett. 87, 086401, 2001