title: Theory of the field-induced BEC in the frustrated spin-1/2 dimer compound BaCuSi2O6.
abstract: Building on recent neutron and NMR experiments, we investigate the field-induced exotic criticality observed in the frustrated compound BaCuSi2O6 using a frustrated model with two types of bilayers. A semiclassical treatment of the effective hard-core boson model shows that perfect interlayer frustration leads to a 2D-like critical exponent varphi=1 without logarithmic corrections and to a 3D low temperature phase with different but nonvanishing triplet populations in both types of bilayers. These further suggest a simple phenomenology in terms of a field-dependent transverse coupling in the context of which we reproduce the entire field-temperature phase diagram with quantum Monte Carlo simulations.
authors.affiliation: Laboratoire de Physique des Solides, Université Paris-Sud, UMR-8502 CNRS, 91405 Orsay, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Laflorencie
authors.forename: Frédéric
authors.initials: F
authors.lastname: Mila