Tiny Sc Allows the Chains to Rattle: Impact of Lu and Y Doping on the Charge-Density Wave in ScV₆Sn₆

Abstract

The kagome metals display an intriguing variety of electronic and magnetic phases arising from the connectivity of atoms on a kagome lattice. A growing number of these materials with vanadium−kagome nets host charge− density waves (CDWs) at low temperatures, including ScV 6 Sn 6 , CsV 3 Sb 5 , and V 3 Sb 2 . Curiously, only the Sc version of the RV 6 Sn 6 materials with a HfFe 6 Ge 6type structure hosts a CDW (R = Gd−Lu, Y, Sc). In this study, we investigate the role of rare earth size in CDW formation in the RV 6 Sn 6 compounds. Magnetization measurements on our single crystals of (Sc,Lu)V 6 Sn 6 and (Sc,Y)V 6 Sn 6 establish that the CDW is suppressed by substituting Sc by larger Lu or Y. Single-crystal X-ray diffraction reveals that compressible Sn−Sn bonds accommodate the larger rare earth atoms within loosely packed R−Sn−Sn chains without significantly expanding the lattice. We propose that Sc provides extra room in these chains crucial to CDW formation in ScV 6 Sn 6 . Our rattling chain model explains why both physical pressure and substitution by larger rare earth atoms hinder CDW formation despite opposite impacts on lattice size. We emphasize the cooperative effect of pressure and rare earth size by demonstrating that pressure further suppresses the CDW in a Lu-doped ScV 6 Sn 6 crystal. Our model not only addresses why a CDW only forms in the RV 6 Sn 6 materials with tiny Sc but also advances our understanding of why unusual CDWs form in the kagome metals.

Tuning charge density wave of kagome metal ScV6Sn6

“…The resistivity values at 2 K are typically 3.1 × 10 −5 Ωcm and 4.5 × 10 −5 Ωcm, and the residual resistivity ratio (RRR = ρ 300K /ρ 2K ) is 3.5 and 3.1 for x = 0.086 and 0.157, respectively. It is important to note that the substitutions of Y and Lu elements at the Sc position also affect the CDW in a similar manner due to the limitation of rattling in the Sc-Sn-Sn chains in substituted samples [29]. The strong electron-phonon coupling, which is the ultimate origin of the CDW, is caused by displacement of Sc and Sn atoms [10,20,32,33].…”

“…The absence of any magnetic order in ScV 6 Sn 6 makes the AHE-like behavior intriguing and opens up further discussion. Both the chemical substitution and pressure tune the Sc-Sn and Sn-Sn bonds distance [26,28,29], leading to the renormalization of imaginary phonon modes and suppression of the CDW. However, the pressures below 2 GPa do not significantly impact the behavior of Hall resistivity, indicating a marginal effect on the electronic instability.…”

“…It is worth noting that the CDW phase of ScV 6 Sn 6 is very fragile without any additional features of superconductivity and magnetism. The application of either internal chemical pressure through doping or external physical pressure can completely suppress the CDW due to minor modifications in the Sc-Sn and Sn-Sn bonds [26,28,29]. The phase remains robust at lower doping levels [26].…”

“…This prompts a speculation of a correlation between CDW and anomalous Hall-like feature. This speculation can be tested by performing pressure-dependent magneto-transport measurements since CDW phase seems to rely on loose Sc-Sn-Sn chains which are highly impacted by pressure [26,28,29]. Owing to several exotic microscopic features associated with the Sc-Sn and Sn-Sn bonds, as well as hidden magnetism related to anomalous Hall-like behavior, it is compelling to investigate that how the anomalous Hall-like behavior is coupled with the CDW phase.…”

Quantum oscillations evidence for topological bands in kagome metal ScV6Sn6

“…The electronic and magnetic properties of RV 6 Sn 6 (R = Tb, Dy, Ho, Er, and Tm) have been studied in [25]. Here we focus on the kagome metal ScV 6 Sn 6 , which is the only one showing a CDW transition in RV 6 Sn 6 family so far [3,26], and its non-trivial topology has been studied by angle-resolved photoemission spectroscopy (ARPES) [27,28] and x-ray scattering [29] measurements. Despite the similarities between AV 3 Sb 5 compounds and ScV 6 Sn 6 , their CDWs have different wave vectors [3,7,21,30], and ScV 6 Sn 6 does not host superconductivity in the ground state [3].…”