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.
@article{arxiv.1607.03231,
title = {Continuous excitations of the triangular-lattice quantum spin liquid YbMgGaO4},
author = {J. A. M. Paddison and M. Daum and Z. L. Dun and G. Ehlers and Y. Liu and M. B. Stone and H. D. Zhou and M. Mourigal},
journal= {arXiv preprint arXiv:1607.03231},
year = {2017}
}
Comments
21 pages, 8 figures, includes Supplementary Information