1211.5522 (F. Casola et al.)

Field-induced quantum soliton lattice in a frustrated two-leg spin-1/2
ladder    [PDF]

F. Casola, T. Shiroka, A. Feiguin, S. Wang, M. S. Grbić, M. Horvatić, S. Krämer, S. Mukhopadhyay, C. Berthier, H. -R. Ott, H. M. Rønnow, Ch. Rüegg, J. Mesot

The field-induced quantum phase transitions (QPT) of the spin ladder material Bi(Cu(1-x)Znx)2PO6 have been investigated via 31P nuclear magnetic resonance (NMR) on single-crystal samples with x = 0 and x = 0.01. Measurements at temperatures between 0.25 K and 20 K in magnetic fields up to 31 T served to establish the nature of the various phases. In BiCu2PO6, an incommensurate (IC) magnetic order develops above a critical field mu0*H(c1) ~ 21 T; the field and temperature dependences of the NMR lines and the resulting model for the spin structure are discussed. Supported by results of Density-Matrix Renormalization Group (DMRG) calculations it is argued that the observed field-induced IC order involves the formation of a magnetic-soliton lattice. An additional QPT is predicted to occur at H > H(c1). For x = 0.01, this IC order is found to be stable against site disorder, although with a renormalized critical field.

View original: http://arxiv.org/abs/1211.5522