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arXiv 1705.00510cond-mat.str-el
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自旋1/2三角反铁磁体中的整体phase diagram和量子自旋液体

Global phase diagram and quantum spin liquids in spin-1/2 triangular antiferromagnet

Shou-Shu Gong, W. Zhu, J. -X. Zhu, D. N. Sheng, Kun Yang

摘要:

利用圆柱几何上的密度矩阵重整化群计算方法,研究了三角形格子上的自旋- $1/2$海森堡模型,其中所有三角形中的三个自旋都具有最近邻$J_1 > 0$、次最近邻$J_2 > 0$海森堡相互作用和附加的标量手征相互作用$J_χ(\vec{S}_i \times \vec{S}_j) \cdot \vec{S}_k$.随着$J_2$($J_2/J_1 \leq 0.3$)和$J_χ$($J_χ/J_1 \leq 1.0$)相互作用的增加,我们建立了一个包含磁有序$120^{\circ}$相、条纹相和非共面四面体相的量子相图。在这些磁序相之间,我们发现了一个手征自旋液体(CSL)相,它被确定为一个$ν= 1/2$玻色子分数量子霍尔态,可能具有自发旋转对称性破缺。通过打开手征相互作用,我们发现,以前确定的$J_1 - J_2$三角形模型($0.08 \lesssim J_2/J_1 \lesssim 0.15$)中的自旋液体显示出在非常小的$J_χ$的CSL相的相变。我们还计算了两种自旋液相中的自旋三重态能隙,有限尺寸的结果表明,在奇数拓扑扇区中能隙很大,而在偶数拓扑扇区中能隙很小或消失。我们讨论了我们的结果的自旋液相的性质的影响。

英文摘要:

We study the spin-$1/2$ Heisenberg model on the triangular lattice with the nearest-neighbor $J_1 > 0$, the next-nearest-neighobr $J_2 > 0$ Heisenberg interactions, and the additional scalar chiral interaction $J_χ(\vec{S}_i \times \vec{S}_j) \cdot \vec{S}_k$ for the three spins in all the triangles using large-scale density matrix renormalization group calculation on cylinder geometry. With increasing $J_2$ ($J_2/J_1 \leq 0.3$) and $J_χ$ ($J_χ/J_1 \leq 1.0$) interactions, we establish a quantum phase diagram with the magnetically ordered $120^{\circ}$ phase, stripe phase, and non-coplanar tetrahedral phase. In between these magnetic order phases, we find a chiral spin liquid (CSL) phase, which is identified as a $ν= 1/2$ bosonic fractional quantum Hall state with possible spontaneous rotational symmetry breaking. By switching on the chiral interaction, we find that the previously identified spin liquid in the $J_1 - J_2$ triangular model ($0.08 \lesssim J_2/J_1 \lesssim 0.15$) shows a phase transition to the CSL phase at very small $J_χ$. We also compute spin triplet gap in both spin liquid phases, and our finite-size results suggest large gap in the odd topological sector but small or vanishing gap in the even sector. We discuss the implications of our results to the nature of the spin liquid phases.

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