Origin of the Anomalous Electrical Transport Behavior in Fe‐Intercalated Weyl Semimetal T_d‐MoTe₂

Abstract

crystals down to few layers and even monolayer. MoTe 2 is a typical member among TMDCs, hosting fascinating electronic properties, such as extremely large magnetoresistance, [6,7] the emergence of superconductivity, [8] the existence of topological Weyl nodes [9][10][11][12] and semiconducting behavior with a finite band gap. [13] Layered structure with weak interlayer coupling allows for the change of layer stacking order and subsequently gives rise to a structural polymorphism. [14][15][16] In fact, MoTe 2 appears in three kinds of structures: the trigonal prismatic coordinated 2H phase (space group P6 3 /mmc), distorted octahedral coordinated structures, including the monoclinic 1T′ (space group P2 1 /m), and the orthorhombic T d (space group Pmn2 1 ) phases. The 2H phase exhibits semiconducting behavior, while 1T′ and T d phases show semimetallic characters. [13,17,18] As shown in Figure 1a, at room temperature, distortion of in-plane bond give rise to monoclinic unit cell 1T′ phase (tilt angle of ≈93.9°). When decreasing the temperature below 250 K, the shift of layer stacking results an orthorhombic structure. [16,19] In its monoclinic 1T′ phase, monolayer MoTe 2 has been proposed to be topological insulator exhibiting quantum spin Hall effect. [3] While the T d phase demonstrates a number of unique properties, such as extremely large magnetoresistance, nontrivial superconductivity, [20][21][22] switchable ferroelectricity, giant nonlinear Hall effect, and unconventional planar spin Weyl semimetal T d -MoTe 2 has recently attracted much attention due to its intriguing electronic properties and potential applications in spintronics. Here, Fe-intercalated T d -Fe x MoTe 2 single crystals (0 < x < 0.15 ) are grown successfully. The electrical and thermoelectric transport results consistently demonstrate that the phase transition temperature T S is gradually suppressed with increasing x. Theoretical calculation suggests that the increased energy of the T d phase, enhanced transition barrier, and more occupied bands in 1T′ phase is responsible for the suppression in T S . In addition, a ρ α -lnT behavior induced by Kondo effect is observed with x ≥ 0.08, due to the coupling between conduction carriers and the local magnetic moments of intercalated Fe atoms. For T d -Fe 0.15 MoTe 2 , a spin-glass transition occurs at ≈10 K. The calculated band structure of T d -Fe 0.25 MoTe 2 shows that two flat bands exist near the Fermi level, which are mainly contributed by the d yz and d x y 2 2 − orbitals of the Fe atoms. Finally, the electronic phase diagram of T d -Fe x MoTe 2 is established for the first time. This work provides a new route to control the structural instability and explore exotic electronic states for transition-metal dichalcogenides.