Incommensurate Spin Dynamics of Underdoped SuperconductorYBa2Cu3O6.7

The spin dynamics of the underdoped superconductor ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{6.7}$ ( $T_c\sim 67\mathrm{K}$) was revealed to have an incommensurate wave vector dependence with “pillars” in the dispersion relation at the positions ( $\frac{1}{2}\pm d,\frac{1}{2},0\mathrm{}$) and ( $\frac{1}{2},\frac{1}{2}\pm d,0\mathrm{}$). This is the same symmetry as that found in ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$. The value of the incommensurability, $d=0.11\mathrm{}\pm 0.01\mathrm{r}.\mathrm{l}.\mathrm{u}\sim \frac{1}{8}$, is very close to the value expected from the hole concentration. These results have demonstrated that the spin dynamics do not depend on the details of Fermi surface but have an analogous form to that for the proposed stripe domain structure.