Evidence for an Intermediate Phase below the Critical Density for the MI transition in silicon MOSFETs*

The magnetoconductivity of the strongly interacting 2D electron system in low disorder silicon MOSFETs is found to scale with B/T throughout the insulating phase, confirming earlier measurements for densities near the metal-insulator transition n_c [1, 2]. We report further that the magnetoconductivity can be collapsed onto a single curve deep in the insulator for all densities up to approximately n* ~ 0.8 n_c. The shape of the scaled curves varies between n* and n_c, where n_c signals the entry into the metallic state. This suggests the presence of an intermediate phase between the deep insulator and the metal.

[1] S. A. Vitkalov, H. Zheng, K. M. Mertes, and M. P. Sarachik, Phys. Rev. Lett. 87, 086401 (2001).
[2] Yeekin Tsui, S. A. Vitkalov, M. P. Sarachik and T. M. Klapwijk, Phys. Rev. B 71, 033312 (2005).