Multiple closely spaced transitions and multi-band Hall response in clean ScV$_6$Sn$_6$

Abstract

The kagome metal ScV$_6$Sn$_6$ has attracted attention as a platform for exploring the interplay between charge density wave (CDW) order and symmetry-breaking phenomena, including a recently reported intermediate phase and a low-field Hall anomaly that has been attributed to an anomalous Hall effect (AHE). The interpretation of both observations has been limited by the modest sample quality achieved by previous growth procedures, which produced crystals with in-plane residual resistivity ratios (RRR) of at most $\approx$9. Here, we report a simple modification of the flux growth procedure that yields ScV$_6$Sn$_6$ single crystals with RRR exceeding 50, more than five times the previous highest reported value, and use this expanded mobility range to revisit both the symmetry and the magnetotransport of the CDW phase. We resolve a sequence of closely spaced transitions in the immediate vicinity of $T_{CDW}$ that emerges above a sharp threshold of RRR $\approx 4$, and demonstrate through elastoresistivity that the intermediate phase breaks the three-fold rotational symmetry of the parent lattice. We examine the Hall response from both the parent samples across the full RRR range as well as Cr-doped samples, and conclude it is quantitatively inconsistent with an intrinsic AHE and is instead explained by ordinary multi-band transport involving small, high-mobility pockets identified through quantum oscillations. These results refine the symmetry-breaking landscape of ScV$_6$Sn$_6$ and establish systematic mobility tuning as a diagnostic for disentangling an intrinsic AHE from multi-band Hall contributions in kagome CDW systems.