Dimensional crossover in self-intercalated antiferromagnetic V5S8 nanoflakes

Electronic and magnetic ordered states are strongly correlated to the dimensions of matter. Here we report a dimensional crossover in self-intercalated antiferromagnetic ${\mathrm{V}}_{5}{\mathrm{S}}_{8}$ nanoflakes. The transition of three-dimensional (3D) to two-dimensional (2D) transport, evidenced by thickness-independent conductivity, occurs when the thickness of ${\mathrm{V}}_{5}{\mathrm{S}}_{8}$ flakes is reduced to \ensuremath{\sim}7.3 nm. At low temperatures, 3D transport follows Fermi liquid behavior, but 2D transport suggests the emergence of Kondo physics with a logarithmic dependence on the temperature and a negative magnetoresistance of a 5.0 nm thick ${\mathrm{V}}_{5}{\mathrm{S}}_{8}$ flake at low temperatures for both in-plane and perpendicular magnetic fields. At temperatures higher than 6 K, the magnetoresistance is positive and parabolically dependent on the magnetic field, indicating suppression of the antiferromagnetic order. Based on a simple magnon gas model, a temperature-independent effective magnon moment $(\ensuremath{\sim}1g{\ensuremath{\mu}}_{B})$ is extracted from the Hall coefficient for all ${\mathrm{V}}_{5}{\mathrm{S}}_{8}$ flakes with different thicknesses. Our results reveal that dimensional crossover plays an important role in tuning the electronic properties in 2D metallic transition-metal dichalcogenides (TMDs).