Line-shape predictions via Bethe ansatz for the one-dimensional spin-1/2 Heisenberg antiferromagnet in a magnetic field
Line-shape predictions via Bethe ansatz for the one-dimensional spin-1/2 Heisenberg antiferromagnet in a magnetic field
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DOI：
10.1103/physrevb.62.14871
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发表时间：
2000-12-01
影响因子：
3.7
通讯作者：
Müller, G
中科院分区：
文献类型：
--
作者：
Karbach, M;Müller, G
一维(1D)S=1/2海森堡反铁磁体基态中平行于外磁场的自旋涨落受一组双参数集体激发的控制。在N个位置和磁化强度为0<；M-z<；N/2的循环链中，包含2m(Z)个自旋的基态被重新组态为不同种类准粒子的物理真空，可以通过Bethe量子数的特征组态在坐标Bethe ansatz的框架内识别。动力学上的主要激发是两个这样的准粒子的散射态。对于N-无穷大，这些集体激发在(q，omega)空间中形成了一个无公度软模的连续体。它们在动态自旋结构因子S-ZZ(q，欧米伽)中的矩阵元素是由有限N的Bethe波函数直接计算出来的。由此得到的线形预测N->；无穷远补充了先前通过代数分析得到的S-Zz(q，欧米伽)在零场极限下精确的两自旋部分的精确结果。它们与强磁场中准一维反铁磁性化合物的中子散射实验有关。
The spin fluctuations parallel to the external magnetic field in the ground state of the one-dimensional (1D) s=1/2 Heisenberg antiferromngnet are dominated by a two-parameter set of collective excitations. In a cyclic chain of N sites and magnetization 0 < M-z < N/2, the ground state, which contains 2M(z) spinons, is reconfigured as the physical vacuum for a different species of quasiparticles, identifiable in the framework of the coordinate Bethe ansatz by characteristic configurations of Bethe quantum numbers. The dynamically dominant excitations are found to be scattering states of two such quasiparticles. For N->infinity these collective excitations form a continuum in (q,omega) space with an incommensurate soft mode. Their matrix elements in the dynamic spin structure factor S-zz(q,omega) are calculated directly from the Bethe wave functions for finite N. The resulting lineshape predictions N->infinity complement the exact results previously derived via algebraic analysis for the exact two-spinon part of S-zz(q,omega) in the zero-field limit. They are relevant for neutron-scattering experiments on quasi-1D antiferromagnetic compounds in a strong magnetic field.