Spin-1/2 XX chain in a transverse field with regularly alternating g factors: Static and dynamic properties

摘要

We consider the spin-1/2 isolropic XY chain in an external magnetic field directed along the z axis with periodically varying g factors. To reveal the effects of regularly alternating g factors, we calculate various static and dynamic equilibrium quantities in the ground state and at finite temperatures. We demonstrate that because of the regularly alternating g factors the saturation field may disappear and the field dependence of the susceptibility in the ground state has additional logarithmic singularity at zero field. Moreover, the zero-field susceptibility has a logarithmic singularity as T → 0. Furthermore, the dynamic structure factors exhibit much more structure in the "wave vector-frequency" plane that can be traced out to modifications of the two-fermion excitation continua which exclusively determine S_(zz)(k, ω) and dominate the properties of S_(xx)(k, ω). We discuss what changes can be observed in dynamic experiments on the corresponding substances.