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arXiv · 1802.09329

Direct observation of multi-spinon excitations outside of the two-spinon continuum in the antiferromagnetic spin chain cuprate Sr2CuO3

J. Schlappa·U. Kumar·K. J. Zhou·S. Singh·M. Mourigal·V. N. Strocov·A. Revcolevschi·L. Patthey·H. M. Rønnow·S. Johnston·T. Schmitt
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Abstract

One-dimensional (1D) magnetic insulators have attracted significant interest as a platform for studying emergent phenomena such as quasiparticle fractionalization and quantum criticality. The antiferromagnetic Heisenberg chain of spins-1/2 is an important reference system; its elementary excitations are spin-1/2 quasiparticles called spinons that are always created in pairs. However, while inelastic neutron scattering (INS) experiments routinely observe the excitation continuum associated with two-spinon states, the presence of more complex dynamics associated with four-spinon states has only been inferred from comparison with theory. Here, we show that resonant inelastic x-ray scattering (RIXS) is capable of accessing the four-spinon excitations directly, in a spectroscopic region separated from the two-spinon continuum. Our results provide the first direct measurement of four-spinon excitations, which is made possible by the fundamentally different correlation functions probed by RIXS compared to INS. This advance holds great promise as a tool in the search for novel quantum states, in particular quantum spin liquids.

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J. Schlappa, U. Kumar, K. J. Zhou, S. Singh, M. Mourigal, V. N. Strocov, A. Revcolevschi, L. Patthey, H. M. Rønnow, S. Johnston, T. Schmitt. 2018-02-26. Direct observation of multi-spinon excitations outside of the two-spinon continuum in the antiferromagnetic spin chain cuprate Sr2CuO3. https://doi.org/10.1038/s41467-018-07838-y

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