Polarons in quantum chains with XY exchange and Dzyaloshinsky-Moriya interaction

A. M. Dikandé ()

The European Physical Journal B: Condensed Matter and Complex Systems, 2007, vol. 55, issue 4, 397-402

Abstract: Excitations of the polaron types are investigated in the spin-1/2 quantum chain with XY exchange and Dzyaloshinsky-Moriya interaction, both coupled to acoustic vibrations of the substrate lattice. The study is carried out via Jordan-Wigner transformation with the help of which the spin chain is mapped onto a chain of spinless fermions. From the resulting effective fermion-lattice Hamiltonian, the discrete equations of motion are derived. These equations are solved in the continuum limit for self-trapped states near the bottom of the fermion spectrum interacting with long-wavelength acoustic lattice modes. The associate polaron solution, which has a pulse shape, is shown to propagate bound to the induced lattice kink distortion by translation along the chain at a constant velocity v. The pair can also experience an additional acceleration ϑ 0 when the free fermion charge is excited above its groundstate. The polaron binding energy is strongly reduced, depending quadratically on the ratio D/J of the Dzyaloshinsky-Moriya interaction strength D to the isotropic XY exchange interaction J. It is also found that polaron parameters depend only on the XY spin-lattice coupling but not on the Dzyaloshinsky-Moriya contribution. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007

Keywords: 63.20.Ry Anharmonic lattice modes; 71.38.-k Polarons and electron-phonon interactions; 75.10.Pq Spin chain models (search for similar items in EconPapers)
Date: 2007
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DOI: 10.1140/epjb/e2007-00075-9

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