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**Authors: **Trinanjan Datta
(Poster Presenter-ASU), Zewei Chen
and Dao-Xin Yao (Sun Yat-sen Univ.)

**
We analyze and compare
the effect of spatial and spin anisotropy on spin conductivity in a two
dimensional S=1/2 Heisenberg quantum magnet on a square lattice. We explore the
model in both the Neel antiferromagnetic (AF) phase and the collinear
antiferromagnetic (CAF) phase. We find that in contrast to the effects of spin
anisotropy in the Heisenberg model, spatial anisotropy in the AF phase does not
suppress the zero temperature regular part of the spin conductivity in the zero
frequency limit - rather it enhances it. We also explore the finite temperature
effects on the Drude weight in the AF phase for various spatial and spin
anisotropy parameters. We find that the Drude weight goes to zero as the
temperature approaches zero. At finite temperatures (within the collision less
approximation) enhancing spatial anisotropy increases the Drude weight value
and increasing spin anisotropy decreases the Drude weight value. In the CAF
phase (within the non-interacting approximation) the zero frequency spin
conductivity has a finite value for non-zero values of the spatial anisotropy
parameter. In the CAF phase increasing the spatial anisotropy parameter
suppresses the regular part of the spin conductivity response at zero frequency.
Furthermore, we find that the CAF phase displays a spike in the spin
conductivity not seen in the AF phase. Inclusion of the smallest amount of spin
anisotropy causes a gap to develop in the spin conductivity response of both
the AF and CAF phase. Based on these studies we conclude that materials with
spatial anisotropy are better spin conductors than those with spin anisotropy
both at zero and finite temperatures. We utilize exchange parameter ratios for
real material systems as inputs to the computation of spin conductivity.**