Extremely large magnetoresistance in the type-II Weyl semimetalMoTe2

Abstract

We performed the angle dependent magnetoresistance (MR), Hall effect measurements, the temperature dependent magneto-thermoelectric power (TEP) S(T) measurements, and the first-principles calculations to study the electronic properties of orthorhombic phase MoTe2 (Td-MoTe2), which was proposed to be electronically two-dimensional (2D). There are some interesting findings about Td-MoTe2: (1) A scaling approach εθ=(sin 2 θ+γ -2 cos 2 θ) 1/2 is applied, where θ is the magnetic field angle with respect to the c axis of the crystal and γ is the mass anisotropy. Unexpectedly, the electronically 3D character with γ as low as 1.9 is observed in Td-MoTe2; (2) The possible Lifshitz transition and the following electronic structure change can be verified around T~150 K and T~60 K, which is supported by the evidence of the slop changing of the temperature dependence of TEP, the carrier density extracted from Hall resistivity and the onset temperature of γ obtained from the MR measurements. The extremely large MR effect in Td-MoTe2 could originate from the combination of the electron-hole compensation and a particular orbital texture on the electron pocket, which is supported by the calculations of electronic structure. Our results may provide a general scaling relation for the anisotropic MR and help to recognize the origins of the MR effect in other systems, such as the Weyl semimetals and the Dirac ones.

Multiple metamagnetism, extreme magnetoresistance and nontrivial topological electronic structures in the magnetic semimetal candidate holmium monobismuthide

“…With the gradual increment of temperature, the metamagnetic behaviors become more and more inconspicuous, and disappear above 6 K. Figure 3(a) shows the variation of zero-field resistivity with temperature for HoBi from 2 to 300 K. As plotted, the resistivity is metallic in nature and decreases monotonically to 2 K, where the resistivity r 0 becomes as small as 2.6 μΩ cm, resulting in a large residual resistivity ratio RRR=ρ(300 K)/ρ(2 K)∼193. In the inset of figure 3(a), the low-temperature resistivity obeys a power-law behavior, ρ(T)=ρ 0 +AT n with n=3.9 similar in numerical value to that of LaSb (n=4), which indicates the interband s-d e-ph scattering, rather than the intraband s-s e-ph scattering should be dominant [6,27]. The low-temperature resistivity is also fitted by the above-mentioned relation with n = 3 (see the supplementary materials is available online at stacks.iop.org/ NJP/21/093063/mmedia).…”

Large nonsaturating magnetoresistance and pressure-induced phase transition in the layered semimetal HfTe2

“…Classically, perfect compensation of electron and hole carriers in semimetals will lead to a large transverse MR with a quadratic field dependence [10]. We note that there are also reports about the large MR materials MoTe 2 and WTe 2 leading to contradictory results concerning the degree * wbensch@ac.uni-kiel.de of carrier compensation, but a strong temperature dependence of the Fermi surface was observed in these studies [11][12][13][14][15][16][17]. For Cd 3 As 2 [3] and WTe 2 [18] the large MR was proposed to occur due to a topological protection of the carriers from backscattering in zero field.…”

Engineering Dirac states in graphene: Coexisting type-I and type-II Floquet-Dirac fermions

“…Due to the excessive tilt, type-II fermion possesses a Fermi surface geometry with hole and electron pockets, which is topologically distinct from point-like Fermi surface for type-I fermion. Exotic properties originating from type-II Weyl/Dirac fermions include Fermi arc surface states, large unsaturated magnetoresistance, and Landau level spectrum squeezing [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Type-I fermions have been found in simple elemental materials of graphene and borophene [19,20], while the candidates with type-II fermions are only discovered in relatively complex materials, including three-dimensional WTe2, MoTe2, PtSe2 [2,4,5,7,10,11,17,21,22], and two-dimensional oxides [23,24].…”