Defect induced ferromagnetic ordering and room temperature negative magnetoresistance in MoTeP (original) (raw)
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Extremely high magnetoresistance and conductivity in the type-II Weyl semimetals WP2 and MoP2
Nature communications, 2017
The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectacular electronic properties such as large mobilities accompanied by extremely high magnetoresistance. In particular, two closely neighboring Weyl points of the same chirality are protected from annihilation by structural distortions or defects, thereby significantly reducing the scattering probability between them. Here we present the electronic properties of the transition metal diphosphides, WP2 and MoP2, which are type-II Weyl semimetals with robust Weyl points by transport, angle resolved photoemission spectroscopy and first principles calculations. Our single crystals of WP2 display an extremely low residual low-temperature resistivity of 3 nΩ cm accompanied by an enormous and highly anisotropic magnetoresistance above 200 million % at 63 T and 2.5 K. We observe a large suppression of charge carrier backscattering in WP2 from transport measurements. These properties are likely a cons...
Evolution of extremely large magnetoresistance in a Weyl semimetal, WTe2 with Ni-doping
Physical Review Materials
WTe 2 , a type-II Weyl semimetal, exhibits extremely large magnetoresistance (XMR) that is attributed to perfect electron-hole compensation. Here, we studied the evolution of the electronic properties of WTe 2 with Ni substitution at W sites. Transport measurements exhibit a metal-to-insulator transition at low temperatures with the application of magnetic field; the field-induced effect is significantly reduced in the doped sample. The XMR of about 10 6 % at 2 K in WTe 2 is reduced to 10 4 % in the 10% Ni-doped sample. The magnetoresistance shows an H 2 dependence and follows the temperature dependence of classical carrier mobility. We observe a deviation from Kohler's rule in both cases, indicating the presence of multiple types of charge carriers. Quantum oscillation data exhibit a signature of four Fermi pockets (two electron and two hole pockets) in both cases, and the nontrivial nature of the electron and hole bands. Interestingly, the electron-hole compensation is nearly perfect even in the doped compound, although the size of the Fermi pockets and the charge-carrier interaction parameters are slightly changed with doping. These results reveal intriguing insight into the XMR behavior of this class of materials and the possibilities of tuning the properties of charge carriers within the XMR regime.
Large magnetoresistance in the type-II Weyl semimetal WP2
Physical Review B
We report magnetotransport study on type-II Weyl semimetal WP2 single crystals. Magnetoresistance (MR) exhibits a nonsaturating H n field dependence (14,300% at 2 K and 9 T) whereas systematic violation of Kohler's rule was observed. Quantum oscillations reveal a complex multiband electronic structure. The cyclotron effective mass close to the mass of free electron me was observed in quantum oscillations along b-axis, while reduced effective mass of about 0.5me was observed in a-axis quantum oscillations, suggesting Fermi surface anisotropy. Temperature dependence of the resistivity shows a large upturn that cannot be explained by the multi-band magnetoresistance of conventional metals. Even though crystal structure of WP2 is not layered as in transition metal dichalcogenides, quantum oscillations suggest partial two-dimensional character.
Extremely high magnetoresistance and conductivity in the type-II Weyl semimetal WP2
2017
The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectacular electronic properties such as large mobilities accompanied by extremely high magnetoresistance. In particular, two closely neighboring Weyl points of the same chirality are protected from annihilation by structural distortions or defects, thereby significantly reducing the scattering probability between them. Here we present the electronic properties of the transition metal diphosphides, WP 2 and MoP 2 , which are type-II Weyl semimetals with robust Weyl points by transport, angle resolved photoemission spectroscopy and first principles calculations. Our single crystals of WP 2 display an extremely low residual lowtemperature resistivity of 3 nΩ cm accompanied by an enormous and highly anisotropic magnetoresistance above 200 million % at 63 T and 2.5 K. We observe a large suppression of charge carrier backscattering in WP 2 from transport measurements. These properties are likely a consequence of the novel Weyl fermions expressed in this compound.
Magnetotransport properties of MoP2
Physical Review B, 2017
We report magnetotransport and de Haas-van Alphen (dHvA) effect studies on MoP2 single crystals, predicted to be type-II Weyl semimetal with four pairs of robust Weyl points located below the Fermi level and long Fermi arcs. The temperature dependence of resistivity shows a peak before saturation, which does not move with magnetic field. Large nonsaturating magnetoresistance (MR) was observed, and the field dependence of MR exhibits a crossover from semicalssical weakfield B 2 dependence to the high-field linear-field dependence, indicating the presence of Dirac linear energy dispersion. In addition, systematic violation of Kohler's rule was observed, consistent with multiband electronic transport. Strong spin-orbit coupling (SOC) splitting has an effect on dHvA measurements whereas the angular-dependent dHvA orbit frequencies agree well with the calculated Fermi surface. The cyclotron effective mass ∼ 1.6me indicates the bands might be trivial, possibly since the Weyl points are located below the Fermi level.
Spin-generation in magnetic Weyl semimetal Co2MnGa across varying degree of chemical order
Applied Physics Letters
Recently discovered magnetic Weyl semimetals (MWSM), with enhanced Berry curvature stemming from the topology of their electronic band structure, have gained much interest for spintronics applications. In this category, Co2MnGa, a room temperature ferromagnetic Heusler alloy, has garnered special interest as a promising material for topologically driven spintronic applications. However, until now, the structural-order dependence of spin current generation efficiency through the spin Hall effect has not been fully explored in this material. In this paper, we study the evolution of magnetic and transport properties of Co2MnGa thin films from the chemically disordered B2 to ordered L21 phase. We also report on the change in spin generation efficiency across these different phases, using heterostructures of Co2MnGa and ferrimagnet Co xTb1− x with perpendicular magnetic anisotropy. We measured large spin Hall angles in both the B2 and L21 phases, and within our experimental limits, we di...
Anisotropy in the electronic transport properties of Weyl semimetal WTe2 single crystals
AIP Advances, 2018
We measure the electrical resistivity ρ of type-II Weyl semimetal WTe 2 using highquality single crystals for the current I along the a and b crystallographic directions in rotating magnetic fields in the plane perpendicular to the current direction. In zero field, ρ exhibits huge anisotropy and the ratio ρ b /ρ a develops with decreasing temperature approaching ∼30 at T = 0. A low-T power-law behavior of ρ∝T n with n = 2.7-2.9 may reflect the characteristic carrier scattering mechanism, probably associated with the strongly T-dependent mobilities, which lead to the sign change in the Hall resistivity. In the Kohler plot, the magnitude of the transverse magnetoresistance (MR) differs by more than two orders of magnitude depending on the Iand B-directions. It also shows clear deviation of MR from the B 2 dependence for all the configurations. No singular directions (magic angles) appear in the rotating B measurements.
Nature Physics, 2015
The Weyl semimetal (WSM) [1] is a novel gapless state with massless relativistic electrons and promises exotic transport properties and surface states [2-4] that are different from those of topological insulators (TIs) [5, 6], another famous topological state. Further, normal semimetals (e.g. WTe 2) [7] start a new trend in recent years to realize the large magnetoresistance, the property of a material in which the electrical resistance changes by an external magnetic field. In this Letter, we choose NbP in magneto-transport experiments, because its band structure assembles the WSM [8, 9] and the normal semimetal together. Such a combination in NbP indeed leads to remarkable transport properties observed, an extremely large magnetoresistance of 850,000 % at 1.85 K (250 % at room temperature) in a magnetic field of 9 T without any signs of saturation and an ultrahigh carrier mobility of 5×10 6 cm 2 V −1 s −1 , accompanied by strong Shubnikov-de Hass (SdH) oscillations. NbP presents a fantastic example to design materials funcitonalities by combining the topological and traditional phases.
Superconductivity in doped Weyl semimetal Mo0.9Ir0.1Te2 with broken inversion symmetry
Superconductor Science and Technology, 2021
This work presents the emergence of superconductivity in Ir—doped Weyl semimetal T d —MoTe2 with broken inversion symmetry. Chiral anomaly induced planar Hall effect and anisotropic magneto-resistance confirm the topological semimetallic nature of Mo 1 − x Ir x Te2. Observation of weak anisotropic, moderately coupled type-II superconductivity in T d -Mo 1 − x Ir x Te2 makes it a promising candidate for topological superconductor.
Superconductivity in Weyl semimetal candidate MoTe2
Nature Communications, 2016
In recent years, layered transition-metal dichalcogenides (TMDs) have attracted considerable attention because of their rich physics [1]; for example, these materials exhibit superconductivity [2,3], charge density waves [4], and the valley Hall effect [5,6]. As a result, TMDs have promising potential applications in electronics, catalysis, and spintronics [7−9]. Despite the fact that the majority of related research focuses on semiconducting TMDs (e.g., MoS 2 [10]), the characteristics of WTe 2 are provoking strong interest in semimetallic TMDs with extremely large magnetoresistance [11], pressure-driven superconductivity [12,13], and the predicted Weyl semimetal (WSM) state [14]. In this work, we investigate the sister compound of WTe 2 , MoTe 2 , which is also predicted to be a WSM [15] and a quantum spin Hall insulator in bulk and monolayer [16] form, respectively. We find that MoTe 2 exhibits superconductivity with a resistive transition