Topological defects in a spin-nematic phase on the triangular lattice

Topological defects play an important role in the theory of nematic phases in liquid crystals. However, relatively little is known about their role in quantum spin nematics[1,2,3]. Here we consider the topological defects which could arise in such a state. The model we consider is the spin-1 bilinear biquadratic model on the triangular lattice, tuned to an SU(3) point[4,5,6]. We classify defects by homotopy theory, and explore how they evolve into the neighboring anti-ferroquadrupolar spin-nematic phase. \\[4pt] [1] B. A. Ivanov, R. S. Khymyn, and A. K. Kolezhuk, Phys. Rev. Lett. 100, 047203 (2008).\\[0pt] [2] T. Grover and T. Senthil, Phys. Rev. Lett. 107, 077203 (2011). \\[0pt] [3] C. Xu and A. W. W. Ludwig, Phys. Rev. Lett, 108, 047202 (2012). \\[0pt] [4] A. Lauchil, F. Mila and K. Penc, Phys. Rev. Lett. 97, 087205 (2006).\\[0pt] [5] H. Tsunetsugu and M. Arikawa, J. Phys. Soc. Jpn. 75, 083701 (2006).\\[0pt] [6] A. Smerald and N. Shannon, arXiv:1307.5131. (accepted for publication in PRB)