Dynamics of the anisotropic two-dimensional XY model |
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Authors: | L S Lima and A ST Pires |
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Institution: | (1) Departamento de Física, Universidade Federal de Minas Gerais, 702, Belo Horizonte, 30123-970, MG, Brazil |
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Abstract: | In this paper we study the dynamics of the two-dimensional XY model with single-ion anisotropy, and spin S = 1, in the large
D phase, and low temperatures, using the bond operator formalism. The in-plane structure factor is a delta function. The out
of plane shows a three peak structure, which merges in a single peak at the Brillouin zone boundary. We analyze also spin
currents generated by a magnetic field gradient. The spin conductivity is calculated, at finite temperature, using the Kubo
formula. The model shows unconventional ballistic spin transport at finite temperature. The computed spin conductivity exhibits
a nonzero Drude weight at finite temperature. For ω< 2m, where m is the energy gap, the spin conductivity is described solely
by the Drude weight. There is a regular contribution to the spin conductivity for ω> 2m, which persist in the zero temperature
limit. The conductivity at the critical point, and for small frequencies, is (gμB)2/ħ times a universal scaling function of ħω/kB T. |
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Keywords: | PACS" target="_blank">PACS 75 40 Gb Dynamic properties 75 10 Jm Quantized spin models |
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