Incommensurate Spin-Peierls Phases in the One-Dimensional Quantum   Isotropic XY Model
  Using the numerical approach for a study of the thermodynamic properties of the nonuniform one-dimensional spin-1/2 isotropic XY model in a transverse field we examine different lattice distortions to reveal which spin-Peierls phases are realized in the magnetic chain at zero temperature in the presence of external field. 
Oleg Derzhko, Taras Krokhmalskii