Multi-carrier transport in ZrTe₅ film

Abstract

The single layer of Zirconium pentatelluride (ZrTe 5 ) has been predicted to be a large-gap two-dimensional (2D) topological insulator, which has attracted particular attention in the topological phase transitions and potential device application. Here we investigated the transport properties in ZrTe 5 films with the dependence of thickness from a few nm to several hundred nm. We find that the temperature of the resistivity anomaly's peak (T p ) is inclining to increase as the thickness decreases, and around a critical thickness of ~40 nm, the dominating carriers in the films change from n-type to p-type. With comprehensive studying of the Shubnikov-de Hass (SdH) oscillations and Hall resistance at variable temperatures, we demonstrate the multi-carrier transport instinct in the thin films. We extract the carrier densities and mobilities of two majority carriers using the simplified two-carrier model. The electron carriers can be attributed to the Dirac band with a non-trivial Berry's phase π, while the hole carriers may originate from the surface chemical reaction or unintentional doping during the microfabrication process. It is necessary to encapsulate ZrTe 5 film in the inert or vacuum environment to make a substantial improvement in the device quality.

Two-Dimensional Quantum Hall Effect and Zero Energy State in Few-Layer ZrTe5

“…Transport is apparently hole dominated at all back-gate voltages and the chemical potential resides deep inside the valence band. This behavior heralds the temperature-induced Lifshitz transition previously reported in the literature 4 , 13 , 16 − 18 (Section 3 and 4, SI ). Figure 1 e displays a color map of ρ xx in the ( V g , T )-plane and confirms this interpretation.…”

“…Complex transport behavior as well as low mobility have been observed in thin films, whereas the intrinsic physics remained elusive. 18 − 21 Here, significant advances in observing the intrinsic magneto-transport properties of thin ZrTe 5 are reported by fabricating and measuring devices without any exposure to ambient air. Clean single band transport, incipient quantum Hall effect behavior, and evidence for a bulk energy gap in this promising quantum spin Hall insulator material are the outcome of these experiments.…”

“…The field effect mobility for holes and electrons is obtained by replotting the data of Figure 1 c on a conductivity ordinate ( Figure S5b, Supporting Information ), using the expression 18 , 25 Here, σ xx is the sheet conductivity, V g is the gate voltage, and is the capacitance per unit area where e is the elementary charge. For our back-gate displaced from the ZrTe 5 by a 300 nm thick SiO 2 layer and a hBN flake, a fit to gate-dependent carrier density data from Hall measurements yields C g = 0.970 F/cm 2 (Section S2, SI ).…”

Optical conductivity and resistivity in a four-band model for ZrTe5 from ab initio calculations

“…ARPES measurements linked this peak to a crossover from p-type to n-type carriers when decreasing temperature [7,[21][22][23], which concurred with a sign change of the Hall number [17,24]. The temperature of the resistivity maximum varied with sample thickness and doping [25][26][27]. Recently, this resistivity peak was also related to the potential topological properties of ZrTe 5 and interpreted as a signature for a transition upon cooling [28] from a WTI to an STI state [29] or the reverse [30], as well as a signature of Dirac polarons [31].…”

Shear lag analysis of I‐shaped structural members

“…Takayanagi et al investigated the shear lag effect of carbon‐fiber reinforced plastic I‐shaped beams based on the modified Reissner's method, and the anisotropic properties of flange material were considered. Gan et al proposed a computation method to analyze the shear lag effect of I‐shaped straight, curved beams based on the energy variation principle, and numerical analysis was also conducted to verify the accuracy of the method. Normally, the differential function of longitudinal displacement or differential function of maximum angular displacement was used as the generalized displacement; however, the physical meaning of the displacements is not clear, which cannot be measured directly.…”