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

TL;DR

This study investigates field-induced quantum phase transitions in a frustrated two-leg spin-1/2 ladder, revealing an incommensurate magnetic order and a magnetic-soliton lattice supported by NMR and DMRG calculations.

Contribution

It provides experimental evidence of a field-induced quantum soliton lattice in a frustrated spin ladder, supported by theoretical DMRG modeling, and explores the effects of site disorder.

Findings

Incommensurate magnetic order develops above ~21 T in BiCu2PO6.

The order involves a magnetic-soliton lattice structure.

Site disorder slightly renormalizes the critical field but preserves the order.

Abstract

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.