Skyrmion and bimeron excitations in bilayer quantum Hall systems

Charged excitations are topological solitons (skyrmions) in quantum Hall systems. They are CP3 skyrmions in the bilayer system, where the underlying symmetry is SU(4). We present a microscopic formulation of CP3 skyrmions in a system where the electron density is imbalanced between the two layers. A skyrmion is constructed by dressing a cloud of SU(4) isospins around an electron or a hole, and it carries the same charge as an electron or a hole at the filling factor ν=1. When the parallel magnetic field penetrates between the two layers, it deforms a skyrmion into a bimeron (a pair of merons). Each meron carries a fractional charge. We calculate the activation energy and show that it decreases rapidly as the parallel magnetic field increases near the balanced point.