Quantum transport in a compensated semimetal W2As3 with nontrivial Z2 indices

Abstract

We report a topological semimetal W2As3 with a space group C2/m. Based on the first-principles calculations, band crossings are partially gapped when spin-orbit coupling is included. The Z2 indices at the electron filling are [1;111], characterizing a strong topological insulator and topological surface states. From the magnetotransport measurements, nearly quadratic field dependence of magnetoresistance (MR) (B [200]) at 3 K indicates an electron-hole compensated compound whose longitudinal MR reaches 11500% at 3 K and 15 T. In addition, multiband features are detected from the high-magnetic-field Shubnikov-de Haas (SdH) oscillation, Hall resistivity, and band calculations. A nontrivial π Berry's phase is obtained, suggesting the topological feature of this material. A twoband model can fit well the conductivity and Hall coefficient. Our experiments manifest that the transport properties of W2As3 are in good agreement with the theoretical calculations.

Angle-dependent magnetoresistance and its implications for Lifshitz transition in W2As3

“…In short, from SdH-oscillation measurements we confirm W 2 As 3 is a topological semimetal. This same conclusion was also drawn by Li et al [38]; there more Fermi sheets with different Berry phases were resolved.…”

“…In conclusion, compared with the previous study in W 2 As 3 [38], besides the large unsaturated MR, more importantly, we first find that the ADMR of W 2 As 3 depends strongly on temperature, and undergoes an obvious deformation from the horizontal dumbbell-like shape above 40 K to the vertical lotus-like pattern below 30 K. Such feature implies a dramatic reconstruction of Fermi surface. Hall effect measurements indicate an abnormal increase in hole carrier density below 40 K, around which thermopower exhibits a large reversal while Nernst coefficient increases abnormally.…”

“…4(c). At 100 K, electron-type carrier density n e dominates, while the mobilities of electron and hole are essentially the same, indicating that at this temperature the system can more or less be regarded as a single-band system, which is in contrast to the majority of hole-type carrier density in the previous report [38]. Lowering temperature, the n e only slightly decreases with T (be noted the log scale of n e,h ) while the n h significantly increases in the temperature range 30 and MoTe 2 semimetals [9,11].…”

“…12) with the angle spanned by a and c being β=124.7 o . For many decades, the physical properties of W 2 As 3 have remained unclear until recently, Li et al reported the large MR and the Shubnikov de Hass (SdH) quantum oscillations [38]. The topological nature was also suggested by first-principles calculation.…”

“…Since systematic SdH studies have been reported recently in Ref. [38], we do not plan to get into too many details. After subtracting a smooth polynomial background from the total resistivity, the remaining part, ρ− ρ , is shown in Fig.…”