Fractional excitations in the square lattice quantum antiferromagnet.
Fractional excitations in the square lattice quantum antiferromagnet.
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DOI：
10.1038/nphys3172
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发表时间：
2015-01-01
期刊：
影响因子：
19.6
通讯作者：
中科院分区：
文献类型：
--
作者：
自量子力学诞生之初，量子磁体就占据了多体理论和真实的材料低温实验之间的沃土。然而，我们对相互作用的自旋-1/2系统的理解，即使是看似简单的系统，也远未完成。例如，量子正方晶格海森堡反铁磁体（QSLHAF）在其磁激发谱中表现出迄今未知的惊人异常。这种量子效应表现为以特定波矢量（π，0）传播的激发。我们使用极化中子能谱充分表征的磁波动的金属有机化合物CFTD，一个已知的实现QSLHAF模型。我们的实验揭示了一个各向同性的激发连续异常，我们分析理论上使用Gutzwiller投影试验波函数。的激发连续占的存在空间扩展对分数S=1/2准粒子，2D类似物的1D自旋。远离反常波矢，这些分数激发被束缚并形成常规的磁振子。我们的结果建立了分数准粒子的存在，在高能量谱的准二维反铁磁体，即使在没有挫折。
Quantum magnets have occupied the fertile ground between many-body theory and low-temperature experiments on real materials since the early days of quantum mechanics. However, our understanding of even deceptively simple systems of interacting spins-1/2 is far from complete. The quantum square-lattice Heisenberg antiferromagnet (QSLHAF), for example, exhibits a striking anomaly of hitherto unknown origin in its magnetic excitation spectrum. This quantum effect manifests itself for excitations propagating with the specific wave vector (π, 0). We use polarized neutron spectroscopy to fully characterize the magnetic fluctuations in the metal-organic compound CFTD, a known realization of the QSLHAF model. Our experiments reveal an isotropic excitation continuum at the anomaly, which we analyse theoretically using Gutzwiller-projected trial wavefunctions. The excitation continuum is accounted for by the existence of spatially-extended pairs of fractional S=1/2 quasiparticles, 2D analogues of 1D spinons. Away from the anomalous wave vector, these fractional excitations are bound and form conventional magnons. Our results establish the existence of fractional quasiparticles in the high-energy spectrum of a quasi-two-dimensional antiferromagnet, even in the absence of frustration.
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影响因子：
8.6
作者：
Coldea, R;Tennant, DA;Tylczynski, Z
通讯作者：
Tylczynski, Z
影响因子：
8.6
作者：
ANDERSON, PW;BASKARAN, G;HSU, T
通讯作者：
HSU, T
影响因子：
8.6
作者：
Guarise, M.;Dalla Piazza, B.;Grioni, M.
通讯作者：
Grioni, M.
影响因子：
--
作者：
Franjic, F;Sorella, S
通讯作者：
Sorella, S
影响因子：
3.7
作者：
Dalla Piazza, B.;Mourigal, M.;Ronnow, H. M.
通讯作者：
Ronnow, H. M.