Rattling Chains Lead to a Charge Density Wave in Kagome Metal ScV₆Sn₆

The connectivity of atoms on a kagome lattice can produce exciting electronic and magnetic behavior. Metallic kagome compounds show intricate magnetism, unusual superconductivity, and structural orders called charge density waves (CDWs). We discovered that the intermetallic compound ScV₆Sn₆ develops a CDW below 92 K [1]. Curiously, none of the other <i>R</i>V₆Sn₆ variants (<i>R</i> = rare earth) develop this phase transition despite their electronic and structural similarities.<br/>We undertook a doping and crystallographic study to examine how substituting Y and Lu for Sc suppresses the CDW in ScV₆Sn₆ [2]. The structural details and doping trends we observed revealed that the small Sc atom in ScV₆Sn₆ leaves extra space needed for the modulated Sn-Sn bonding critical to the CDW. Replacing Sc with larger rare earths removes the extra space for these displacements, stifling CDW formation. Our model addresses why ScV₆Sn₆ is the only member of its family to form a structural modulation.<br/><br/>[1] H. W. S. Arachchige, et al. Phys. Rev. Lett. <b>129</b>, 216402 (2022) https://doi.org/10.1103/PhysRevLett.129.216402<br/>[2] W. R. Meier, et al. J. Am. Chem. Soc. <b>145</b> (38), 20943 (2023) https://doi.org/10.1021/jacs.3c06394