Alternation of sign of magnetization current in driven XXZ chains with twisted XY boundary gradients
Alternation of sign of magnetization current in driven XXZ chains with twisted XY boundary gradients
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具有扭曲 XY 边界梯度的驱动 XXZ 链中磁化电流符号的交替
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
V. Popkov
中科院分区：
文献类型：
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作者：
V. Popkov
我们研究了一个开放的XXZ自旋1/2链驱动的平衡耦合与边界水库针对不同的自旋取向在XY平面。模型的对称性显示，这似乎是不同的自旋链的奇数和偶数的大小。其结果是，自旋电流被发现与链长交替，排除了弹道输运的可能性。由于另一种整体对称性，热传输被完全切断。此外，我们调查模型的数值和分析。在强耦合下，我们用微扰理论找到了一个精确的非平衡定态。通过求解保证微扰膨胀自洽性的长期条件来确定状态。我们发现在临界区磁化电流与自旋链各向异性Δ之间存在非平凡的依赖关系|Δ| < 1的窄间隙时，扭转角沿着增大3倍。
We investigate an open XXZ spin 1/2 chain driven out of equilibrium by coupling with boundary reservoirs targeting different spin orientations in the XY-plane. Symmetries of the model are revealed which appear to be different for spin chains of odd and even sizes. As a result, the spin current is found to alternate with chain length, ruling out the possibility of ballistic transport. Heat transport is switched off completely by virtue of another global symmetry. Further, we investigate the model numerically and analytically. At strong coupling, we find an exact nonequilibrium steady state using perturbation theory. The state is determined by solving secular conditions which guarantee self-consistency of the perturbative expansion. We find nontrivial dependence of the magnetization current on the spin chain anisotropy Δ in the critical region |Δ| < 1, and a phenomenon of tripling of the twisting angle along the chain for narrow lacunae of Δ.