کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1803412 | 1024617 | 2009 | 7 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Delocalized 2-magnons eigenstates in long-range correlated random Heisenberg chains Delocalized 2-magnons eigenstates in long-range correlated random Heisenberg chains](/preview/png/1803412.png)
We consider the one-dimensional quantum disordered S=12 Heisenberg ferromagnetic chain model with long-range correlated exchange couplings and study the nature of collective two-spin excitations. By using an exact diagonalization of the Hamiltonian in the two-spin flip subspace, we compute the spin wave participation number to characterize the localized or delocalized nature of the two-magnon states. For strongly correlated random exchange couplings, extended two-spin excitations with finite energy appear. Integrating the time-dependent Schroedinger equation, we follow the time-evolution of an initially localized two-spin state. We find that, associated with the emergence of extended spin waves, the wave-packet mean-square displacement develops a ballistic spread. Further, the single-spin wave-packet acquires an asymmetric profile due to the kinematic interaction between the excited spins.
Journal: Journal of Magnetism and Magnetic Materials - Volume 321, Issue 15, August 2009, Pages 2304–2310