Study of the electronic properties of topological kagome metals YV$_6$Sn$_6$ and GdV$_6$Sn$_6$

Abstract

The synthesis and characterization of vanadium-based kagome metals YV 6 Sn 6 and GdV 6 Sn 6 are presented. X-ray diffraction, magnetization, magnetotransport, and heat capacity measurements reveal an ideal kagome network of V-ions coordinated by Sn and separated by triangular lattice planes of rareearth ions. The onset of low-temperature, likely noncollinear, magnetic order of Gd spins is detected in GdV 6 Sn 6 , while V-ions in both compounds remain nonmagnetic. Density functional theory calculations are presented modeling the band structures of both compounds, which can be classified as Z 2 topological metals in the paramagnetic state. Both compounds exhibit high mobility, multiband transport and present an interesting platform for controlling the interplay between magnetic order associated with the R-site sublattice and nontrivial band topology associated with the V-based kagome network. Our results invite future exploration of other RV 6 Sn 6 (R=rare earth) variants where this interplay can be tuned via R-site substitution.

Uniaxial ferromagnetism in the kagome metal TbV${_6}$Sn${_6}$

“…An intriguing question is whether the Ising ferromagnetism in TbV 6 Sn 6 may lead to the formation of exotic phases, such as Chern gapped Dirac fermions in the bulk, or a quantum anomalous Hall surface state. Previous density functional theory calculations suggested that the electronic structures of several RV 6 Sn 6 compounds can be characterized as that of a topological metal, with surface states originating from the non-trivial Z 2 indices associated with the occupied bands [12]. Our ARPES measurements are consistent with others that have revealed bulk bands with Dirac dispersion near the K point of the Brillouin zone [15].…”

“…The microstructure parameters derived from the refinement are listed in Table I. The derived crystal structure is consistent with previous measurements of the rare-earth substituted GdV 6 Sn 6 and YV 6 Sn 6 [12].…”

“…YV 6 Sn 6 , which is nearly identical to TbV 6 Sn 6 except the rare-earth site has been replaced with an ion with no 4f electrons, has been measured recently and found to have no magnetic order or evident magnetic anisotropy down to 1.7K [12]. Thus the cause of the ferromagnetic phase transition in TbV 6 Sn 6 is from the cooperative alignment of the 4f electrons of the Tb 3+ ion.…”

“…A similar set of materials, but with non-magnetic V substituted for Mn in the intermetallic T site, might very well promise similar physics with a cleaner separation of magnetic and electronic subsystems. Recently GdV 6 Sn 6 and YV 6 Sn 6 have been experimentally investigated [12,13], with the Gd member undergoing ferromagnetic order at 5K, and a calculated band structure suggestive of hosting non-trivial topological phases. In addition, ScV 6 Sn 6 was found to undergo a charge density wave phase transition reminiscent of the CsV 3 Sb 5 system [14].…”