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arXiv 0909.2728cond-mat.str-el
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XXZ模型中的准粒子

Quasiparticles in the XXZ model

Ping Lu, Gerhard Muller, Michael Karbach

摘要:

本文分析了一维自旋为1/2的链的XXZ模型的坐标Bethe近似解,着重讨论了准粒子的统计性质。重点是给称为XX,XXX和伊辛模型,在相当大的简化发生的特殊情况。XXZ谱可以从不同的赝真空中产生,作为具有不同排斥统计的准粒子集合的配置。这些集合是互补的,因为一个集合的伪真空包含来自另一个集合的最大数量的粒子。XXX模型的Bethe弦解在平面和轴向区域演化不同。在伊辛极限,他们成为铁磁领域与整数值的排斥统计。在XX极限,它们分裂成具有(有效)费米统计的硬核玻色子。两组准粒子自旋1/2和分数统计的区别,其中一组(自旋)产生的XXZ谱从唯一的,关键的基态实现在平面政权,和另一组(孤子)产生相同的频谱从双重的,反铁磁有序的基态实现在轴向政权。在伊辛极限,孤子成为反铁磁畴壁。

英文摘要:

The coordinate Bethe ansatz solutions of the XXZ model for a one-dimensional spin-1/2 chain are analyzed with focus on the statistical properties of the constituent quasiparticles. Emphasis is given to the special cases known as XX, XXX, and Ising models, where considerable simplifications occur. The XXZ spectrum can be generated from separate pseudovacua as configurations of sets of quasiparticles with different exclusion statistics. These sets are complementary in the sense that the pseudovacuum of one set contains the maximum number of particles from the other set. The Bethe ansatz string solutions of the XXX model evolve differently in the planar and axial regimes. In the Ising limit they become ferromagnetic domains with integer-valued exclusion statistics. In the XX limit they brake apart into hard-core bosons with (effectively) fermionic statistics. Two sets of quasiparticles with spin 1/2 and fractional statistics are distinguished, where one set (spinons) generates the XXZ spectrum from the unique, critical ground state realized in the planar regime, and the other set (solitons) generates the same spectrum from the twofold, antiferromagnetically ordered ground state realized in the axial regime. In the Ising limit, the solitons become antiferromagnetic domain walls.

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