Magnetic field induced bound states in spin-$\frac{1}{2}$ ladders

Abstract

Motivated by the intriguing mode splittings in a magnetic field recently observed with inelastic neutron scattering in the spin ladder compound (C${}_5$H${}_{12}$N)${}_2$CuBr${}_4$ (BPCB), we investigate the nature of the spin ladder excitations using DMRG and analytical arguments. Starting from the fully frustrated ladder, for which we derive the low-energy spectrum, we show that bound states are generically present close to $k=0$ in the dynamical structure factor of spin ladders above $H_{c1}$, and that they are characterized by a field-independent binding energy and an intensity that grows with $H-H_{c1}$. These predictions are shown to explain quantitatively the split modes observed in BPCB.

6 pages, 4 figures + 8 pages, 9 figures (in Supplementary Material)

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Cited by in corpus (1)

• Investigating field-induced magnetic order in Han Purple by neutron scattering up to 25.9 T