Evidence of a magnetic Bose glass in (CH3) 2 CHNH3 Cu (Cl {0.95} Br {0.05}) 3 from neutron diffraction

We report the single-crystal study of the bulk magnetization and neutron-scattering measurements on a quantum S=1/2 spin ladders system IPA-Cu (Cl0.95 Br0.05) 3 with quenched disorder. In zero field, the disordered spin liquid phase is preserved as in pure IPA-CuCl3. Due to the bond randomness, a different Bose glass phase was directly observed in Hc <H< H′, which separates the spin liquid phase from the unconventional Bose-Einstein condensation phase. The observed finite value of boson compressibility (dM/dH) and lack of field-induced three-dimensional long-range order are consistent with the theoretical prediction.