Quantum spin liquids

• Published in: Science (American Association for the Advancement of Science) Vol. 367; no. 6475
• Main Authors: Broholm, C., Cava, R. J., Kivelson, S. A., Nocera, D. G., Norman, M. R., Senthil, T.
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 17.01.2020; AAAS
• Subjects: Approximation; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Degrees of freedom; Dimers; Dirac equation; Electrodynamics; Elementary excitations; Energy theory; Excitation; Fractions; Gases; Gauge theory; Ground state; Inelastic scattering; Ions; Lattices (mathematics); Magnetic flux; Mathematical models; Neutron flux; Neutron scattering; NMR; Nuclear magnetic resonance; Organic chemistry; Phases; Properties (attributes); Quantum entanglement; Quantum mechanics; Ruthenium; Salts; Spin liquid; Superconductivity; Symmetry; Topology; Wave functions
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.aay0668

Materials with interacting quantum spins that nevertheless do not order magnetically down to the lowest temperatures are candidates for a materials class called quantum spin liquids (QSLs). QSLs are characterized by long-range quantum entanglement and are tricky to study theoretically; an even more difficult task is to experimentally prove that a material is a QSL. Broholm et al. take a broad view of the state of the field and comment on the upcoming challenges. Science , this issue p. eaay0668 Spin liquids are quantum phases of matter with a variety of unusual features arising from their topological character, including “fractionalization”—elementary excitations that behave as fractions of an electron. Although there is not yet universally accepted experimental evidence that establishes that any single material has a spin liquid ground state, in the past few years a number of materials have been shown to exhibit distinctive properties that are expected of a quantum spin liquid. Here, we review theoretical and experimental progress in this area.