Flux-Line Lattice Distortion in $\mathrm{P}\mathrm{r}\mathrm{O}{\mathrm{s}}_4\mathrm{S}{\mathrm{b}}_{12}$

We report that the flux-line lattice in the cubic superconductor $\mathrm{Pr}\mathrm{O}{\mathrm{s}}_4{\mathrm{S}\mathrm{b}}_{12}$ is strongly distorted from an ideal hexagonal lattice at very low temperatures in a small applied field. We attribute this to the presence of gap nodes in the superconducting state on at least some Fermi-surface sheets.

Figure 1

Panel (a) shows the difference between the $XY$ detector images recorded at 0.2 T and zero field, averaged over several rocking angles of the field and sample (contours are drawn at 0.25, 0.5, 1, 1.5, 2, 2.5, 3, and 3.5 counts/hour/pixel [$1\mathrm{\text{detector pixel}}=(8\mathrm{m}\mathrm{m}{)}^2$]). The region immediately around the straight through beam is masked from the image. Panel (b) shows the integrated intensity of the upper right-hand peak as a function of the rotation angle of the sample and field about the vertical ($Y$) axis. The line is a Gaussian function.

Figure 2

The field and temperature dependence of $\beta$, the angle between two reciprocal lattice vectors of the FLL. The vertical bars through the points indicate half of the angular width (FWHM) of the peak intensities on the multidetector.