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arXiv 1407.0318cond-mat.str-el
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扩展的自旋1/2三角海森堡模型中的无隙自旋液相

Gapless spin-liquid phase in an extended spin 1/2 triangular Heisenberg model

Ryui Kaneko, Satoshi Morita, Masatoshi Imada

摘要:

本文从最简单的只考虑最近邻交换作用的等边晶格出发,对三角晶格上的海森堡模型进行了数值研究。我们发现,通过包括一个额外的弱次近邻相互作用,一个量子自旋液体相是稳定的反铁磁秩序。自旋间隙(三重激发间隙)和自旋相关性在长距离衰减代数与反铁磁相和自旋液相之间的临界点处的系统尺寸的增加。这种代数行为在自旋液相中也继续存在,表明存在以动力学和反常临界指数$z+η\sim1$为特征的非常规临界(代数自旋液相)相。在布里渊区的扩展点中发现的异常小的三重态和单重态激发能对这种代数自旋液体施加了限制。

英文摘要:

We numerically study the Heisenberg models on triangular lattices by extending it from the simplest equilateral lattice with only the nearest-neighbor exchange interaction. We show that, by including an additional weak next-nearest-neighbor interaction, a quantum spin-liquid phase is stabilized against the antiferromagnetic order. The spin gap (triplet excitation gap) and spin correlation at long distances decay algebraically with increasing system size at the critical point between the antiferromagnetic phase and the spin-liquid phase. This algebraic behavior continues in the spin-liquid phase as well, indicating the presence of an unconventional critical (algebraic spin-liquid) phase characterized by the dynamical and anomalous critical exponents $z+η\sim1$. Unusually small triplet and singlet excitation energies found in extended points of the Brillouin zone impose constraints on this algebraic spin liquid.

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