QUANTUM HALL-EFFECT IN DOUBLE-QUANTUM-WELL SYSTEMS

We investigate the nature of the electron ground state of a double-quantum-well system in a strong perpendicular magnetic field by using finite-size numerical studies on spherical systems. Interwell electron tunneling is explicitly included by taking into account the spreading of the electron wave function in the direction perpendicular to the double quantum well. As a function of interwell separation, the overlap between the exact ground state of a finite-size system and the Jastrow-type variational wave function is calculated for filling factors v = 1, 2/3, and 1/2. Our results show (a) the destruction of the v = 1 integral quantum Hall effect due to electron-electron interaction; (b) the switching of the ground state from one quantum Hall state to another due to the competition between interwell tunneling and electron correlation; and (c) the possibility of observing the v = 1/2 fractional quantum Hall effect in a double-quantum-well system at appropriate well separations.