Thickness-Dependent Magnetoresistance, Hall Effect, and Nernst Effect in h-BN Encapsulated WTe₂ Flakes: Insights into Carrier Dynamics and Topological Band Structures

High Resolution Image Download MS PowerPoint Slide Tungsten ditelluride (WTe 2 ) is a semimetal of the TMDC group, and one of its most intriguing features is its unsaturated enormous magnetoresistance (MR) at low temperatures. Here, we present the thickness-dependent MR, Hall effect, and Nernst effect of exfoliated flakes of WTe 2 encapsulated by two h-BN layers as a function of magnetic field ( B ) at various temperatures. The MR increased significantly from 8.0 × 10 2 % to 3.3 × 10 3 % with increasing thickness from 43 to 116 nm, which is well explained by the thickness-dependent carrier densities and mobilities determined from the two-band model fitting of the B -dependences of longitudinal resistivity (ρ xx ) and Hall resistivity (ρ xy ). The Nernst coefficient ( S xy ) also showed remarkable enhancement with increasing flake thickness. The maximum value of S xy was 220 μV/K with a temperature gradient of 0.06 K/μm. The measured values of S xy are higher than those in various earlier reports related to TMDCs for a similar structure. The S xy – B characteristic curves exhibited sharp bending features in contrast to the ρ xy – B curves, which showed more gradual changes. The devices also showed a nonlinear signal for the Nernst effect at different temperature gradients. These behaviors are likely related to the unique band structures, which include compensated electron and hole bands as well as topologically nontrivial Weyl points.