Suppression of magnetoresistance in thin $WTe_2$ flakes by surface oxidation

Thickness dependent electronic structure in WTe$_2$ thin films

“…This not only explains the decease of carrier density as the sample is made thinner as reported in Refs. [25,26] but also suggests it is possible to open a band gap and realize the 2D topological insulator in even thin samples, as predicted by theory [20]. In addition, the quadratic MR also shows a crossover from 3D to 2D behavior as the samples are made thinner, while gating is shown to affect both the quadratic MR and the quantum oscillations of a thin sample by tuning its carrier density.…”

“…Electron and hole compensation is found in samples down to thickness around 10 nm, but the MR of thin films is suppressed significantly due to surface scattering from amorphous surface oxides [25,26,[29][30][31]. Meanwhile the carrier density also has been observed to decrease as the samples are made thinner [25,26], which is unexpected if it is assumed that thin film samples are simply thinner cases of 3D bulk samples. Recently optical and transport measurements in thin film samples with thickness from 9 to 11.7 nm suggests a band gap could open in monolayer sample and this is supported by band structure calculations [32].…”

“…The studies of the unusual MR of bulk WTe 2 has been extended to thin film samples [23][24][25][26][27][28]. Electron and hole compensation is found in samples down to thickness around 10 nm, but the MR of thin films is suppressed significantly due to surface scattering from amorphous surface oxides [25,26,[29][30][31].…”

“…The studies of the unusual MR of bulk WTe 2 has been extended to thin film samples [23][24][25][26][27][28]. Electron and hole compensation is found in samples down to thickness around 10 nm, but the MR of thin films is suppressed significantly due to surface scattering from amorphous surface oxides [25,26,[29][30][31]. Meanwhile the carrier density also has been observed to decrease as the samples are made thinner [25,26], which is unexpected if it is assumed that thin film samples are simply thinner cases of 3D bulk samples.…”

Temperature effect on lattice and electronic structures of WTe2 from first-principles study

“…The rapid decrease of MR at high temperature is explained by the decrease of the carrier mobilities. 22 However, as we know, the temperature can also modify the lattice structure, meanwhile, Te-5p and W-5d orbitals are spatially extended, thus making it very sensitive to structural variations. 9,23 Therefore, to check whether the thermal expansion and the related band-structure change response for the highly sensitive temperature-dependence of MR is an interesting problem, which we address in the present work.…”