Japan Atomic Energy Agency, Spring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan.
J Phys Condens Matter. 2010 Oct 13;22(40):403201. doi: 10.1088/0953-8984/22/40/403201. Epub 2010 Sep 14.
Recent developments of theoretical studies on spin nanotubes are reviewed, especially focusing on the S = 1/2 three-leg spin tube. In contrast to the three-leg spin ladder, the tube has a spin gap in the case of the regular-triangle unit cell when the rung interaction is sufficiently large. The effective theory based on the Hubbard Hamiltonian indicates a quantum phase transition to a gapless spin liquid due to the lattice distortion to an isosceles triangle. This is also supported by the numerical diagonalization and the density matrix renormalization group analyses. Furthermore, combining analytical and numerical approaches, we reveal several novel magnetic-field-induced phenomena: Néel, dimer, chiral and/or inhomogeneous orders, a new mechanism for the magnetization plateau formation, and others. The recently synthesized spin tube materials are also briefly introduced.
本文回顾了近年来关于自旋纳米管的理论研究进展，特别关注 S=1/2 三足自旋管。与三腿自旋梯相比，当梯相互作用足够大时，正则三角形单元的管在有自旋能隙。基于 Hubbard 哈密顿量的有效理论表明，由于晶格变形为等腰三角形，会发生到无能隙自旋液体的量子相变。数值对角化和密度矩阵重整化群分析也支持这一结论。此外，通过结合分析和数值方法，我们揭示了一些新的磁场诱导现象：奈尔、二聚体、手性和/或非均匀有序、形成磁化平台的新机制等。最近合成的自旋管材料也被简要介绍。
