authors:
Oleg Derzhko and
Taras Krokhmalskii
Institute for Condensed Matter Physics, NASU
1 Svientsitskii Str., L'viv-11, 79011, Ukraine
The magnetic relaxation in quantum spin chains received considerable interest from both theoretical and experimental points of view. In our study we discuss an impurity spin relaxation in the quantum spin chain at different temperatures in the presence of an external field.
For this purpose we consider the s=1/2 isotropic XY chain in a transverse (z) field with a single impurity spin placed either in the bulk or at the boundary of the system. Using the Jordan-Wigner transformation we map the spin chain onto a system of noninteracting fermions and calculate numerically the time-dependent xx and zz spin correlation functions of the impurity spin.
The theoretical analysis of impurity dynamics in the considered spin model reported by J. A. Tjon [1] refers to the boundary impurity in the weak-coupling limit.
In the recent study of J. Stolze and M. Vogel [2] an exhaustive analysis of the xx/zz dynamic autocorrelations of bulk/boundary impurity in the absence of external field has been reported. In our study we extend the latter results considering the case of nonzero external (transverse) field. Computing the dynamic autocorrelations for different values of i) the strength of impurity spin interaction with host spins, ii) the transverse field, and iii) the temperature we find new types of long-time asymptotic behavior.
This study was performed within the framework of the STCU project # 1673.
[1] J. A. Tjon, Phys. Rev. B 2, 2411 (1970).
[2] J. Stolze and M. Vogel, Phys. Rev. B 61, 4026 (2000).