Quantum Hall ferromagnet in a two-dimensional electron gas coupled with quantum dots

We have studied the magnetoresistance in the two-dimensional electron gas (2DEG) coupled with quantum dots. The structures consist of asymmetrically doped GaAs double quantum wells separated by tunneling GaxAl1-xAs barrier of 50 Å width. On the top of the structure the hexagonal superlattice of the antidots with periodicity View the MathML source and diameter View the MathML source was patterned in the PMMA resist, which was then covered by the gold gate. When the negative gate voltage is applied, potential of the neighbor antidots is overlapped, and the array of disconnected quantum dots with triangular shape has been formed in the top quantum well. Therefore, bilayer system is transformed to the single layer of electrons, which is strongly coupled with quantum dots separated by tunneling barrier. We observed the sudden jump in the magnetoresistance at filling factor 3, which also reveals a pronounced hysteresis. The data may signal an quantum Hall ferromagnetism associated with pseudospin (layer) ferromagnetic order.