Tomas Stephen Northam de la Fuente

Defect structures and spin correlations in disorder-induced quantum spin liquids

Entanglement defines the essential non-classical features of quantum mechanics, and long-range entanglement engenders exotic phenomena such as fractional quantum numbers and emergent topological excitations. Theoretically, the exemplars of such massive long-range entanglement are quantum spin liquids (QSLs), states of quantum magnets in which electronic spins reside in macroscopic superpositions of infinitely many microstates. Recently it has been shown that for spin-ice materials, such as Ho2Ti2O7, it is possible to tune to QSLs via the controlled introduction of structural disorder. We have grown large single crystals of Ho2Ti2O7 in which we are able to control the structural disorder through doping. The defect structures have been studied with neutron Laue diffraction using SXD at ISIS and will be compared with first-principles density-functional calculations to determine the effects on the single-ion magnetic properties. In addition, the spin correlations have been measured using the diffuse scattering of polarized neutrons using D7 at the ILL.