Magnetization plateau of the quantum spin nanotube

The S=12 three-leg spin nanotube is theoretically investigated, using the numerical diagonalization and the density matrix renormalization group (DMRG) calculation. The system has a magnetization plateau at 13 of the saturation magnetization for sufficiently large rung interaction. We mainly focus on the effect of the asymmetric distortion from the regular triangle to the isosceles one. We find an anomalous increase of the plateau width near the symmetric point (i.e., regular triangle) when the asymmetric parameter is varied.