Abstract
Layered van der Waals semimetallic -WTe, exhibiting intriguing properties which include non-saturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as a model topological type-II Weyl semimetal system. Here, ∼45 nm thick mechanically exfoliated flakes of -WTe are studied via atomic force microscopy, Raman spectroscopy, low-T/high- magnetotransport measurements and optical reflectivity. The contribution of anisotropy of the Fermi liquid state to the origin of the large positive transverse and the signature of chiral anomaly of the type-II Weyl Fermions are reported. The samples are found to be stable in air and no oxidation or degradation of the electronic properties is observed. A transverse ∼1200 % and an average carrier mobility of 5000 cmVs at for an applied perpendicular field are established. The system follows a Fermi liquid model for and the anisotropy of the Fermi surface is concluded to be at the origin of the observed positive MR. Optical reflectivity measurements confirm the anisotropy of the electronic behaviour. The relative orientation of the crystal axes and of the applied electric and magnetic fields is proven to determine the observed chiral anomaly in the in-plane magnetotransport. The observed chiral anomaly in the WTe flakes is found to persist up to , a temperature at least four times higher than the ones reported to date.
Highlights
Introduction published maps and institutional affilThe presence of accidental two-fold degeneracies in the electronic band structures of solids leads to linear energy dispersions in the vicinity of the energy-degenerate points or nodes [1,2,3]
The WTe2 flakes are fabricated via mechanical exfoliation from a bulk crystal obtained commercially from hqgraphene
This is in contrast to the μ0 Hcj reported for bulk crystals of Weyl semimetals (WSM)-I where the carrier mobilities were found to be as high as 5 × 106 cm2 /V.s at T = 5 K, leading to μ0 Hcj ≤ 1 T [64,67]
Summary
The WTe2 flakes are fabricated via mechanical exfoliation from a bulk (mother) crystal obtained commercially from hqgraphene The metallic contact pads ing and the transfer of the samples into the cryostat for measurements is achieved in less in van der Pauw 4-probe geometry are obtained by rinsing away the photoresist with than 30 minutes, thereby ensuring minimal oxidation of the flakes. This fabrication protocol warm acetone for 15 seconds in an ultrasonic bath. The geometry of the studied flakes is described by l and w, while the c−axis is the one perpendicular to the plane of the flakes
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