PHENOMENOLOGICAL UNDERSTANDING OF A TRANSPORT REGIME WITH REFLECTION SYMMETRY IN THE QUANTUM HALL SYSTEM IN A COMPOSITE-FERMION PICTURE

In this paper, we present a phenomenological picture based on the comp osite fermion theory, in response to the recent discovery by Shahar et al. [Science 274, 589 (1996)] of a transport regime near the transiti on from a v=1 quantum Hall liquid to a Hall insulator. In this picture , the seemingly unexpected reflection symmetry in the longitudinal res istivity rho(xx) can be understood clearly as due to the symmetry of t he gap excitations which dominate sigma(xx) across the transition, and the abrupt change in sigma(xy) at the transition. The parameter alpha in the linear fit of v(0)(T) of Shahar et al. is also given a simple physical meaning, and the effective mass can be calculated from alpha, which gives a reasonable value of several-electron band mass. When ta king into account the result of network model, the almost invariant Ha ll resistivity rho(xy) across the transition is also well understood.