European X-Ray Free-Electron Laser Facility GmbH, Holzkoppel 4, 22869, Schenefeld, Germany.
Photon Science Division, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland.
Nat Commun. 2018 Dec 19;9(1):5394. doi: 10.1038/s41467-018-07838-y.
One-dimensional (1D) magnetic insulators have attracted significant interest as a platform for studying quasiparticle fractionalization, quantum criticality, and emergent phenomena. The spin-1/2 Heisenberg chain with antiferromagnetic nearest neighbour interactions is an important reference system; its elementary magnetic excitations are spin-1/2 quasiparticles called spinons that are created in even numbers. However, while the excitation continuum associated with two-spinon states is routinely observed, the study of four-spinon and higher multi-spinon states is an open area of research. Here we show that four-spinon excitations can be accessed directly in SrCuO using resonant inelastic x-ray scattering (RIXS) in a region of phase space clearly separated from the two-spinon continuum. Our finding is made possible by the fundamental differences in the correlation function probed by RIXS in comparison to other probes. This advance holds promise as a tool in the search for novel quantum states and quantum spin liquids.
一维（1D）磁性绝缘体作为研究准粒子分数化、量子临界点和新兴现象的平台引起了广泛关注。具有反铁磁最近邻相互作用的自旋-1/2 Heisenberg 链是一个重要的参考体系；其基本磁激发是自旋-1/2 的准粒子，称为自旋子，它们以偶数个形式产生。然而，尽管与双自旋子态相关的激发连续体通常是可观察到的，但对四自旋子和更高阶多自旋子态的研究仍是一个开放的研究领域。在这里，我们通过共振非弹性 X 射线散射（RIXS）在与双自旋子连续体明显分离的相空间区域中直接证明了 SrCuO 中四自旋子激发的存在。RIXS 与其他探针相比，在探测相关函数方面存在根本差异，这使得我们的发现成为可能。这一进展有望成为寻找新型量子态和量子自旋液体的工具。
