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首页> 外文期刊>Physical review >Quasiparticle breakdown in the quasi-one-dimensional Ising ferromagnet CoNb_2O_6
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Quasiparticle breakdown in the quasi-one-dimensional Ising ferromagnet CoNb_2O_6

机译：准一维伊辛铁磁体CoNb_2O_6中的准粒子击穿

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摘要

We present experimental and theoretical evidence that an interesting quantum many-body effect-quasiparticle breakdown-occurs in the quasi-one-dimensional spin-1/2 Ising-like ferromagnet CoNb_2O_6 in its paramagnetic phase at high transverse field as a result of explicit breaking of spin inversion symmetry. We propose a quantum spin Hamiltonian capturing the essential one-dimensional physics of CoNb_2O_6 and determine the exchange parameters of this model by fitting the calculated single-particle dispersion to the one observed experimentally in applied transverse magnetic fields. We present high-resolution inelastic neutron scattering measurements of the single-particle dispersion which observe "anomalous broadening" effects over a narrow energy range at intermediate energies. We propose that this effect originates from the decay of the one particle mode into two-particle states. This decay arises from (ⅰ) a finite overlap between the one-particle dispersion and the two-particle continuum in a narrow energy-momentum range and (ⅱ) a small misalignment of the applied field away from the direction perpendicular to the Ising axis in the experiments, which allows for nonzero matrix elements for decay by breaking the Z_2 spin inversion symmetry of the Hamiltonian.
机译：我们提供的实验和理论证据表明，在高横向磁场中，由于明显的断裂，在顺磁相中的准一维自旋1/2 Ising型铁磁体CoNb_2O_6中发生了有趣的量子多体效应-准粒子击穿自旋反转对称性。我们提出了一种量子自旋哈密顿量，它捕获了CoNb_2O_6的一维基本物理特征，并通过将计算得出的单粒子色散与在施加的横向磁场中实验观察到的单粒子色散拟合来确定该模型的交换参数。我们提供了单粒子分散体的高分辨率非弹性中子散射测量结果，该结果在中等能量的狭窄能量范围内观察到“异常扩大”效应。我们提出，这种效应源自一个粒子模式向两个粒子状态的衰减。这种衰减是由于（ⅰ）在窄的能量动量范围内单粒子分散体和两粒子连续体之间的有限重叠和（ⅱ）远离垂直于Ising轴方向的施加场的未对准引起的。实验中，通过打破哈密顿量的Z_2自旋反转对称性，允许非零矩阵元素衰减。

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