Raman spectroscopic evidence of impurity‐induced structural distortion in SmB 6

Impurity‐induced structural distortion in SmB 6 is suggested by Raman spectroscopy study on impurity‐controlled samples. Significant differences in the Raman spectra of single crystals SmB 6 (6N), synthesized with 99.9999%‐pure boron, and SmB 6 (3N), synthesized with 99.9%‐pure boron, are detected. While no noticeable differences are detected in the X‐ray diffraction of SmB 6 (3N) and SmB 6 (6N), all the Raman phonon modes of the T 2g , E g , and A 1g of SmB 6 (3N) are clearly broader and shift to higher wavenumbers than those of SmB 6 (6N), and the T 2g and E g modes of SmB 6 (3N) show doublet features. Based on the high‐pressure Raman measurements and phonon calculation in uniaxial compression model, we argue that small amount of impurities in SmB 6 (3N) is enough to induce anisotropic distortion in the B 6 octahedra, leading to peculiar behaviors in Raman spectrum of SmB 6 (3N). Our results may present a clue for understanding the current puzzles about SmB 6 of various origins with different impurities.