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arXiv · 1607.03231

Continuous excitations of the triangular-lattice quantum spin liquid YbMgGaO4

J. A. M. Paddison·M. Daum·Z. L. Dun·G. Ehlers·Y. Liu·M. B. Stone·H. D. Zhou·M. Mourigal
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Abstract

A quantum spin liquid (QSL) is an exotic state of matter in which electrons' spins are quantum entangled over long distances, but do not show symmetry-breaking magnetic order in the zero-temperature limit. The observation of QSL states is a central aim of experimental physics, because they host collective excitations that transcend our knowledge of quantum matter; however, examples in real materials are scarce. Here, we report neutron-scattering measurements on YbMgGaO4, a QSL candidate in which Yb3+ ions with effective spin-1/2 occupy a triangular lattice. Our measurements reveal a continuum of magnetic excitations - the essential experimental hallmark of a QSL - at very low temperature (0.06 K). The origin of this peculiar excitation spectrum is a crucial question, because isotropic nearest-neighbor interactions do not yield a QSL ground state on the triangular lattice. Using measurements of the magnetic excitations close to the field-polarized state, we identify antiferromagnetic next-nearest-neighbor interactions in the presence of planar anisotropy as key ingredients for QSL formation in YbMgGaO4.

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J. A. M. Paddison, M. Daum, Z. L. Dun, G. Ehlers, Y. Liu, M. B. Stone, H. D. Zhou, M. Mourigal. 2016-07-12. Continuous excitations of the triangular-lattice quantum spin liquid YbMgGaO4. https://doi.org/10.1038/nphys3971

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