Theory of spin-density profile and lattice distortion in the magnetization plateaus of ${\mathrm{SrCu}}_2{(\mathrm{B}\mathrm{O}}_3{)}_2$

The two-dimensional spin-gap system ${\mathrm{SrCu}}_2({\mathrm{BO}}_3{)}_2$ shows unique physical properties due to the low-dimensionality character and the strong quantum fluctuations. Experimentally, $1/8,1/4,\mathrm{and}1/3$ plateaus have been observed in the magnetization curve under magnetic fields up to 70 T, and the 1/2 plateau is expected to be stabilized at higher magnetic fields. We argue that spin-lattice effects are necessary to describe the spin density profile at the plateaus, and we propose a simple microscopic model of spins interacting adiabatically with the lattice to reproduce the main features of the recent experimental results by nuclear magnetic resonance.