Observation of Bose-Einstein condensation of triplons in quasi 1D spin-gap system Pb2V3O9

We observed a field-induced magnetic ordering in the quasi one-dimensional anti ferromagnetic alternating chain system Pb2V3O9 for the first time. The characteristic temperature dependence of the magnetic susceptibility below T-N and the power law behavior of phase boundary between paramagnetic and ordered phases in the Pb2V3O9 system can be comprehended in terms of Bose-Einstein condensation of triplons, as in the case of TlCuCl3 [Phys. Rev. Lett. 84 (2000) 58681. Our results indicate that BEC of triplons can be observed in the present strongly-coupled-dimer system, while TlCuCl3 is a weak inter dimer coupling system.