铁磁螺旋阶梯海森堡梯子中的自旋能隙和弦序参量：量子蒙特卡罗研究
Spin gap and string order parameter in the ferromagnetic spiral staircase heisenberg ladder: a quantum Monte Carlo study.
作者信息
Brünger C, Assaad F F, Capponi S, Alet F, Aristov D N, Kiselev M N
机构信息
Institut für Theoretische Physik, Universität Würzburg, D-97074 Würzburg, Germany.
出版信息
Phys Rev Lett. 2008 Jan 11;100(1):017202. doi: 10.1103/PhysRevLett.100.017202. Epub 2008 Jan 7.
We consider a spin-1/2 ladder with a ferromagnetic rung coupling J perpendicular and inequivalent chains. This model is obtained by a twist (theta) deformation of the ladder and interpolates between the isotropic ladder (theta=0) and the SU(2) ferromagnetic Kondo necklace model (theta = pi). We show that the ground state in the (theta, J perpendicular) plane has a finite string order parameter characterizing the Haldane phase. Twisting the chain introduces a new energy scale, which we interpret in terms of a Suhl-Nakamura interaction. As a consequence we observe a crossover in the scaling of the spin gap at weak coupling from delta/J parallel proportional, variant J perpendicular/J parallel for theta < theta c approximately 8 pi/9 to delta/J parallel proportional, variant (J perpendicular/J parallel)2 for theta > theta c. Those results are obtained on the basis of large scale quantum Monte Carlo calculations.
我们考虑一个具有垂直铁磁梯级耦合(J)且链不等价的自旋(1/2)梯子。该模型通过对梯子进行扭转（(\theta)）变形得到，并在各向同性梯子（(\theta = 0)）和(SU(2))铁磁近藤项链模型（(\theta = \pi)）之间进行插值。我们表明，在（(\theta)，(J)垂直）平面中的基态具有表征霍尔丹相的有限弦序参量。扭转链引入了一个新的能量尺度，我们根据苏尔 - 中村相互作用对其进行解释。因此，我们观察到在弱耦合下自旋能隙的标度存在交叉，从(\theta < \theta_c \approx 8\pi/9)时(\Delta/J)平行与(J)垂直/(J)平行成比例变化，到(\theta > \theta_c)时(\Delta/J)平行与((J)垂直/(J)平行()^2)成比例变化。这些结果是基于大规模量子蒙特卡罗计算得到的。
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