Field-Induced Double Dome And Bose-Einstein Condensation In The Crossing Quantum Spin Chain System Agvoaso4

We present inelastic neutron-scattering data on the quantum paramagnet AgVOAsO4 that establish this system as a S = 1/2 alternating spin chain compound and provide a direct measurement of the spin gap Delta = 1.2meV. We also present experimental evidence for two different types of field-induced magnetic order between mu 0H(c1) = 8.4T and mu H-0(c2) = 48.9 T, which may be related to Bose-Einstein condensation (BEC) of triplons. Thermodynamic measurements in magnetic fields up to 60 T and temperatures down to 0.1 K reveal a H - T phase diagram consisting of a dome encapsulating two ordered phases with maximum ordering temperatures of 3.8 and 5.3 K, respectively. This complex phase diagram is not expected for a single-(Q) over right arrow BEC system and therefore establishes AgVOAsO4 as a promising multi-(Q) over right arrow Q BEC candidate capable of hosting exotic vortex phases.