Density matrix renormalization group and numerical diagonalization study on the quantum spin nanotube in magnetic field

Sakai, Toru; Sato, Masahiro*; Okunishi, Koichi*; Okamoto, Kiyomi*; Itoi, Chigaku*

The spin tube has attracted a lot of interest as a magnet with a nanotube structure. Various applicable functions of the spin tube are expected to be induced by high magnetic field. The S=1/2 three-leg spin tube has a spin gap due to the strong frustration. Using the numerical dyagonalization and the density matrix renormalization group (DMRG) calculation, we revealed new quantum phase transitions between the spin-gap and gapless phases induced by an asymmetric interchain interactions. Under high magnetic field this system also exhibits some interesting phenomena. The same numerical analysis on the magnetization process indicates that the 1/3 magnetization plateau appears for sufficiently large rung interaction caused by two different mechanisms, depending on the asymmetry. A field induced symmetry breaking accompanied by the chiral order is also revealed to occur.