- Doping, pressure and isotope effects on the pseudogap in rare-earth based high-temperature superconductors by neutron spectroscopic measurements of the relaxation rates of crystal-field excitations. The observation of large upward shifts of the pseudogap temperature upon copper and oxygen isotope substitution  as well as pressure application points to the importance of lattice effects for the understanding of the pseudogap phenomenon.
- Vortex structure and spin dynamics in high-temperature superconductors. By means of small-angle neutron scattering (SANS) we have been able to observe vortex lattices in all doping regimes of La2-xSrxCuO4. In the overdoped regime a field-induced transition from hexagonal to square coordination at around 0.4 Tesla was observed  which is indicative of in-plane anisotropies such as those provided by a d-wave order parameter or the presence of stripes.
- Field-induced quantum phase transitions in the Cu2+ dimer compounds ACuCl3 (A=K, Tl) which exhibit a singlet-triplet energy gap in zero field. At a critical field Hc the lowest components of the Zeeman split triplet (which can be regarded as diluted bosons) intersect the ground-state singlet, thus Bose-Einstein condensation is expected to occur. The magnetic excitation spectrum associated with the condensate has been theoretically predicted to be a gapless Goldstone mode which we verified by inelastic neutron scattering experiments .
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 Ch. Rüegg et al., Nature 423, 62 (2003).