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Experiments on a nearly spin degenerate two-dimensional electron system reveals unusual hysteretic and relaxational transport in the fractional quantum Hall effect regime. The transition between the spin-polarized (with fill fraction $ u = 1/3$) and spin-unpolarized ($ u = 2/5$) states is accompanied by a complicated series of hysteresis loops reminiscent of a classical ferromagnet. In correlation with the hysteresis, magnetoresistance can either grow or decay logarithmically in time with remarkable persistence and does not saturate. In contrast to the established models of relaxation, the relaxation rate exhibits an anomalous divergence as temperature is reduced. These results indicate the presence of novel two-dimensional ferromagnetism with a complicated magnetic domain dynamic.
Magneto-transport measurements are performed on the two-dimensional electron system (2DES) in an AlGaAs/GaAs heterostructure. By increasing the magnetic field perpendicular to the 2DES, magnetoresistivity oscillations due to Landau quantisation can b
We provide a theoretical framework for the electric field control of the electron spin in systems with diffusive electron motion. The approach is valid in the experimentally important case where both intrinsic and extrinsic spin-orbit interaction in
The relaxations of conductivity have been studied in a strongly disordered two-dimensional (2D) electron system in Si after excitation far from equilibrium by a rapid change of carrier density n_s at low temperatures T. The dramatic and precise depen
What are the ground states of an interacting, low-density electron system? In the absence of disorder, it has long been expected that as the electron density is lowered, the exchange energy gained by aligning the electron spins should exceed the enha
The relaxations of conductivity after a temporary change of carrier density n_s during the waiting time t_w have been studied in a strongly disordered two-dimensional electron system in Si. At low enough n_s < n_g (n_g - the glass transition density)