Figure 2. Conversions between skyrmions and antiskyrmions.

The top panels show the snapshots of the magnetization configuration at four selected times corresponding to the vertical lines in the middle and bottom panels; the middle panels show the time evolution of the average spin components m_x, m_y, m_z; the bottom panels show the time evolution of the skyrmion number Q_s. (a), Conversion between a skyrmion and a skyrmion with identical out-going helicity: the D in the sample is 3.5 mJ m⁻²; the background points +z; a current density of 3 × 10¹² A m⁻² (the value is of the input or output side, similarly hereinafter) is applied along −x for 0 ns < t < 0.56 ns followed by a relaxation (highlighted by the gray shadows) until t = 1 ns. (b), Conversion between a skyrmion and a skyrmion with opposite in-going helicity: the D is 3.5 mJ m⁻² in the input side and −3.5 mJ m⁻² in the output side, while a gradient transition from 3.5 mJ m⁻² to −3.5 mJ m⁻² is set in the narrow channel; the background points +z; a current density of 3 × 10¹² A m⁻² is applied along −x for 0 ns < t < 0.51 ns and then is the relaxation until t = 1 ns. (c), Conversion between a skyrmion and an anti-skyrmion with opposite in-going helicity: the D in the sample is 3.5 mJ m⁻²; the background of the input side points +z, while it points −z in the output side; a current density of 2.67 × 10¹² A m⁻² is applied along −x for 0 ns < t < 0.51 ns followed by a relaxation until t = 1 ns. (d), Conversion between a skyrmion and an anti-skyrmion with identical out-going helicity: the profile of D is the same as that in b and the profile of background is the same as that in c; a current density of 2.67 × 10¹² A m⁻² is applied along −x for 0 ns < t < 0.51 ns followed by a relaxation until t = 1 ns. The color scale has been used throughout this paper.