Magnetization process of random quantum spin chains - art. no. 134420

The magnetization process of spin chains with randomness is discussed. We e mphasize a close analogy between these systems and disordered particle syst ems and pay particular attention to the (in)stability of spin-gapped phases against several types of randomness. Generically, spin-gap states (plateau s) and Bose-glass-like localized states compete and stable plateaus are pos sible only for special magnetizations determined by spin S and the period o f a pure system. When no external field is applied, the random-singlet stat e or the Griffith's phase is possible.