Dear  Prof.Matthias<br><br>Let&#39;s taking DM interaction in z-direction, so we have (SxSy-SySx) , which gives an imaginary part <br>1/4i{(S+S+)-(S+S-)-(S-S+)+(S-S-)}. <br><br>I have no idea how to deal with it.<br><br><br>
-------<br>Best Regards<br>Javad Vahedi,<br><br>