We explore theoretically the magnetoresistvity of three-dimensional Weyl and Dirac semimetals in transversal magnetic fields within two alternative models of disorder: (i) short-range impurities and (ii) charged (Coulomb) impurities. Impurity scattering is treated using the self-consistent Born approximation. We find that an unusual broadening of Landau levels leads to a variety of regimes of the resistivity scaling in the temperature-magnetic field plane. In particular, the magnetoresitance is non-monotonous for the white-noise disorder model. For $H\to 0$ the magnetoresistance for short-range impurities vanishes in a non-analytic way as $H^{1/3}$. In the limits of strongest magnetic fields $H$, the magnetoresistivity vanishes as $1/H$ for pointlike impurities, while it is linear and positive in the model with Coulomb impurities.
Giant anisotropic magnetoresistance and planar Hall effect in the Dirac semimetal Cd3As2
各向异性磁电阻是指材料的电阻随电流和外磁场相互方向的变化趋势。在这里，我们报告的实验观察狄拉克半金属Cd 3 As 2的巨各向异性磁电阻及其横向版本，称为平面霍尔效应。相对各向异性磁电阻为负，在2K和10 T下可达-68%。在这种各向同性和双折射材料中的高各向异性和负号归因于沿磁场的场依赖电流，其可以由能带结构的Berry曲率引起。这一观测不仅揭示了外尔和狄拉克半金属中的异常物理现象，而且发现了外尔和狄拉克费米子除了负磁阻之外的其他输运特征。
We investigate the tunneling magnetoresistance in magnetic tunnel junctions (MTJs) comprised of Weyl semimetal contacts. We show that chirality-magnetization locking leads to a gigantic tunneling magnetoresistance ratio, an effect that does not rely on spin filtering by the tunnel barrier. Our results indicate that the conductance in the anti-parallel configuration is more sensitive to magnetization fluctuations than in MTJs with normal ferromagnets, and predicts a TMR as large as 10^4 % when realistic magnetization fluctuations are accounted for. In addition, we show that the Fermi arc states…
We study the effect of random potential created by different types of impurities on the transverse magnetoresistance of Weyl semimetals. It is shown that the magnetic field and temperature dependence of magnetoresistance is strongly affected by the type of impurity potential. Two limiting cases are analyzed in detail: ($i$) the ultra-quantum limit, when the applied magnetic field is so high that only the zeroth and first Landau levels contribute to the magnetotransport, and ($ii$) the semiclassical situation, for which a large number of Landau levels comes into play. A formal diagrammatic appr…
Magnetoresistance and anomalous Hall effect in micro-ribbons of the magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$
磁性外尔半金属由于其特殊的能带结构而表现出有趣的输运现象。最近的实验表明，在shandite型Co $_3$ Sn $_2$ S $_2$块体晶体，这种材料系统是一种磁性外尔半金属。为了获得与手性输运相关的长度尺度，必须制造这种迷人化合物的微观结构。因此，我们已经削减微带（典型尺寸$0.3~\times~3~\times~50$ μ $m^3$）从钴$_3$锡$_2$ S $_2$单晶使用Ga $^{2+}$ -离子的聚焦束，并研究了样品尺寸和可能的表面掺杂对磁输运性质的影响。在微带中观察到的大的本征反常霍尔效应与体样品中的本征反常霍尔效应定量一致。我们的研究结果表明，聚焦离子束切割可用于纳米图案化单晶Co $_3$ Sn $_2$ S $_2$，使未来的运输实验在复杂的微观结构，这Weyl半金属。
Large intrinsic anomalous Hall effect (AHE) due to the Berry curvature in magnetic topological semimetals is attracting enormous interest due to its fundamental importance and technological relevance. Mechanisms resulting in large intrinsic AHE include diverging Berry curvature in Weyl semimetals, anticrossing nodal rings or points of non-trivial bands, and noncollinear spin structures. Here we show that a half-topological semimetal (HTS) state near a topological critical point can provide a new mechanism for driving an exceptionally large AHE. We reveal this through a systematic experimental …
The semiclassical transport theory is especially powerful for investigating galvanomagnetic effects. Generally, the semiclassical theory is applicable only in weak fields because it does not consider Landau quantization. Herein, we extend the conventional semiclassical theory by considering Landau quantization through the field dependence of carrier density in semimetals. The extended semiclassical theory is applicable even in strong fields, where Landau quantization is noticeable. Using this new approach, we explain the qualitative change in the angular dependence of transverse magnetoresista…
Giant Domain-Wall Hall Magnetoresistance in Magnetic Topological Semimetal
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University（华南师范大学）
Observation of linear magnetoresistance and planar Hall effect in the Dirac semimetal PdTe
Institute of Nano Science and Technology（印度纳米科学与技术研究所）；Indian Institute of Science Education and Research Mohali（印度科学教育研究学院莫哈利分校）；Indian Institute of Technology Ropar（印度技术学院罗帕尔分校）
We theoretically investigated the magnetoresistance (MR) and planar Hall effect (PHE) in Weyl semimetals based on the semiclassical Boltzmann theory, focusing on the fine structure of the band dispersion. We identified that the negative longitudinal MR and sign change in the PHE occur because of the negative off-diagonal effective-mass with no topological effects or chiral anomaly physics. Our results highlight the crucial role of the off-diagonal effective-mass, which can cause anomalous galvanomagnetic effects. We propose that the PHE creates a dip in their temperature dependence, which enab…
Negative magnetoresistance is rare in non-magnetic materials. Recently, a negative magnetoresistance has been observed in the quantum limit of $β$-Ag$_2$Se, where only one band of Landau levels is occupied in a strong magnetic field parallel to the applied current. $β$-Ag$_2$Se is a material that host a Kramers Weyl cone with band degeneracy near the Fermi energy. Kramers Weyl cones exist at time-reversal invariant momenta in all symmorphic chiral crystals, and at a subset of these momenta, including the $Γ$ point, in non-symmorphic chiral crystals. Here, we present a theory for the negative m…
Topological materials with extremely large magnetoresistance exhibit a prognostic feature of resistivity turn-on behaviour. This occurs when the temperature dependence of resistivity changes from metallic to semiconducting characteristics on application of external magnetic field above a threshold value. Here, we study the magneto-transport properties of type-II Weyl Semimetal WP2. We find that semi-classical theories of magnetoresistance are consistent with our data without the need to invoke topological surface states. Our findings in this work provides an alternative basis to understand the…
Controlling the electronic properties via bandstructure engineering is at the heart of modern semiconductor devices. Here, we extend this concept to semimetals where, utilizing LuSb as a model system, we show that quantum confinement lifts carrier compensation and differentially affects the mobility of the electron and hole-like carriers resulting in a strong modification in its large, non-saturating magnetoresistance behavior. Bonding mismatch at the heteroepitaxial interface of a semimetal (LuSb) and a semiconductor (GaSb) leads to the emergence of a novel, two-dimensional, interfacial hole …
Quantum Oscillations and Magnetoresistance in Type-II Weyl Semimetals - Effect of a Field Induced Charge Density Wave
最近的实验表明，在强磁场作用下，第二类Weyl半金属如WTe $_2$、MoTe $_2$、Mo $_x$ W $_{1-x}$ Te $_2$和WP $_2$具有显著的输运性质，包括极大的磁电阻和不寻常的温度依赖性。在这里，我们调查磁输运通过Kubo公式在一个极小模型的II型Weyl半金属考虑到电荷密度波（CDW）过渡的影响，这可能会出现，即使在弱耦合在一个强磁场的存在下，因为特殊的朗道级色散的II型Weyl系统。与实验测量一致，我们发现一个非常大的磁阻接近$B^2$缩放在粒子空穴补偿，而在极端的量子极限有一个过渡到一个定性的新的缩放约$B^{0.75}$。我们还研究了Shubnikov-de Haas效应，发现在CDW转变温度以下，电阻率量子振荡的幅度大大增强，这伴随着不寻常的非单调（非Lifshitz-Kosevich）温度依赖性。
Time-reversal symmetry breaking allows for a rich set of magneto-transport properties related to electronic topology. Focusing on the magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$, we prepared micro-ribbons and investigated their transverse and longitudinal transport properties from 100 K to 180 K in magnetic fields $μ_0 H$ up to 2T. We establish the presence of a magnetoresistance (MR) up to 1 % with a strong anisotropy depending the projection of $H$ on the easy-axis magnetization, which exceeds all other magnetoresistive effects. Based on detailed phenomenological modeling, we attribute the obs…
Magnetotransport such as the giant magnetoresistance and Hall effect lies at the heart of fundamental physics and technologies. Recently, some experiments have clearly demonstrated linear magnetotransport (LMT) proportional to magnetic field but the underlying physical mechanism is still unclear. In this work, we show that Berry curvature effect is a new mechanism dominating the LMT. The Berry-curvature-induced LMT widely exists in 66 out of 122 magnetic point groups. For typical magnetic Weyl semimetals Co$_3$Sn$_2$S$_2$ and ferromagnetic MnBi$_2$Te$_4$, Berry curvature induces LMT conductivi…
Layered van der Waals semimetallic $T_\mathrm{d}$-WTe$_{2}$, exhibiting intriguing properties which include non-saturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as model topological type-II Weyl semimetal system. Here, $\sim$45 nm thick mechanically exfoliated flakes of $T_\mathrm{d}$-WTe$_{2}$ are studied $via$ atomic force microscopy, Raman spectroscopy, low-$T$/high-$μ_{0}H$ magnetotransport measurements and optical reflectivity. The contribution of anisotropy of the Fermi liquid state to the origin of the large positive transverse $\mathrm{MR}_\per…
We propose a mechanism to generate dissipationless current in time reversal symmetry breaking Weyl semimetals through the anomalous chiral magnetic effect (ACME). The ACME current is induced by chiral imbalance and flows along the direction of the Weyl nodes separation in momentum space. In contrast to the chiral magnetic effect, the ACME is not related to the chiral anomaly and does not require external magnetic field. In the presence of parallel electric and magnetic fields, the ACME gives rise to an antisymmetric linear magnetoresistance and a planar Hall conductivity, which we estimate to …
