We report the detailed electronic structure of WTe$_2$ by high resolution angle-resolved photoemission spectroscopy. Unlike the simple one electron plus one hole pocket type of Fermi surface topology reported before, we resolved a rather complicated Fermi surface of WTe$_2$. Specifically, there are totally nine Fermi pockets, including one hole pocket at the Brillouin zone center $Γ$, and two hole pockets and two electron pockets on each side of $Γ$ along the $Γ$-$X$ direction. Remarkably, we have observed circular dichroism in our photoemission spectra, which suggests that the orbital angular momentum exhibits a rich texture at various sections of the Fermi surface. As reported previously for topological insulators and Rashiba systems, such a circular dichroism is a signature for spin-orbital coupling (SOC). This is further confirmed by our density functional theory calculations, where the spin texture is qualitatively reproduced as the conjugate consequence of SOC. Since the backscattering processes are directly involved with the resistivity, our data suggest that the SOC and the related spin and orbital angular momentum textures may be considered in the understanding of the anomalous magnetoresistance of WTe$_2$.
The rapidly expanding class of quantum materials known as {\emph{topological semimetals}} (TSM) display unique transport properties, including a striking dependence of resistivity on applied magnetic field, that are of great interest for both scientific and technological reasons. However, experimental signatures that can identify or discern the dominant mechanism and connect to available theories are scarce. Here we present the magnetic susceptibility ($χ$), the tangent of the Hall angle ($\tanθ_H$) along with magnetoresistance in four different non-magnetic semimetals with high mobilities, Nb…
We report a study of physical properties of two quasi-low dimensional metals YNiC$_2$ and LuNiC$_2$ including the investigation of transport, magnetotransport, galvanomagnetic and specific heat properties. In YNiC$_2$ we reveal two subsequent transitions associated with the formation of weakly coupled charge density wave at $T_{CDW}$ = 318 K, and its locking in with the lattice at $T_1$ = 275 K. These characteristic temperatures follow the previously proposed linear scaling with the unit cell volume, demonstrating its validity extended beyond the lanthanide-based $R$NiC$_2$. We also find that,…
A magnetic field parallel to an electrical current does not produce a Lorentz force on the charge carriers. Therefore, orbital longitudinal magnetoresistance is unexpected. Here we report on the observation of a large and non saturating magnetoresistance in lightly doped SrTiO$_{3-x}$ independent of the relative orientation of current and magnetic field. We show that this quasi-isotropic magnetoresistance can be explained if the carrier mobility along all orientations smoothly decreases with magnetic field. This anomalous regime is restricted to low concentrations when the dipolar correlation …
We explore the electronic and topological properties of single crystal SrAl$_2$Si$_2$ using magnetotransport experiments in conjunction with first-principle calculations. We find that the temperature-dependent resistivity shows a pronounced peak near 50 K. We observe several remarkable features at low temperatures, such as large non-saturating magnetoresistance, Shubnikov-de Haas oscillations and cusp-like magneto-conductivity. The maximum value of magnetoresistance turns out to be 459\% at 2 K and 12 T. The analysis of the cusp-like feature in magneto-conductivity indicates a clear signature …
VSe 2是一种过渡金属硫族化物，其具有已被充分研究的电荷密度波跃迁。我们报告的电阻率在低温回升，并在温度低于此电阻率的最小值，一个不寻常的磁阻，这是负的，在低场和正的，在较高的领域，在单晶的VSe 2。负磁电阻随磁场的变化呈抛物线型，且几乎不随角度变化。在高于电阻率最小值的温度下的磁阻总是正的。我们将这些结果解释为VSe 2中近藤效应的特征。磁化率的上升表明存在层间V离子，其可以提供在近藤效应中散射传导电子所需的局部磁矩。的热容量的低温行为，包括高值的伽马，随着偏离居里-外斯定律中观察到的低温磁化率，是一致的与存在的磁性之间的相互作用的顺磁性层间V离子和近藤筛选这些V时刻。
The change of a material's electrical resistance (R) in response to an external magnetic field (B) provides subtle information for the characterization of its electronic properties and has found applications in sensor and storage related technologies. In good metals, Boltzmann's theory predicts a quadratic growth in magnetoresistance (MR) at low B, and saturation at high fields. On the other hand, a number of nonmagnetic materials with weak electronic correlation and low carrier concentration for metallicity, such as inhomogeneous conductors, semimetals, narrow gap semiconductors and topologic…
Electronic flat band systems are a fertile platform to host correlation-induced quantum phenomena such as unconventional superconductivity, magnetism and topological orders. While flat band has been established in geometrically frustrated structures, such as the kagome lattice, flat band-induced correlation effects especially in those multi-orbital bulk systems are rarely seen. Here we report negative magnetoresistance and signature of ferromagnetic fluctuations in a prototypical kagome metal CoSn, which features a flat band in proximity to the Fermi level. We find that the magnetoresistance i…
Colossal Magnetoresistance and Phonon Driven Exchange Dynamics in Eu$_5$Sn$_2$As$_6$
University of Tokyo（东京大学）；University of California, Berkeley（加州大学伯克利分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；National High Magnetic Field Laboratory, Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室国家高磁场实验室）；Molecular Foundry, Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室分子发现中心）；Physikalisch-Technische Bundesanstalt（德国物理技术联邦研究院）
Magnetically coupled charge-transport crossover and giant negative magnetoresistance in iodine-incorporated Cr$_2$Se$_3$
Indian Association for the Cultivation of Science（印度科学文化研究所）；Lomare Technologies Limited（Lomare科技有限公司）；Indian Institute of Technology Tirupati（蒂鲁帕蒂印度理工学院）；Brno University of Technology（布尔诺理工大学）；UGC-DAE Consortium for Scientific Research（UGC-DAE科学研究联盟）；Bose Institute（博斯研究所）；Central European Institute of Technology（中欧技术研究所）；Sincrotrone Trieste s.c.p.a.（的里雅斯特同步辐射中心）
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 report a detailed magnetotransport study on single crystals of PrBi. The presence of $f$-electrons in this material raises the prospect of realizing a strongly correlated version of topological semimetals. PrBi shows a magnetic field induced metal insulator transition below $T \sim 20$ K and a very large magnetoresistance ($\approx 4.4 \times 10^4~$) at low temperatures ($T= 2$ K). We have also probed the Fermi surface topology by de Haas van Alphen (dHvA) and Shubnikov de Haas (SdH) quantum oscillation measurements complimented with density functional theory (DFT) calculations of the band …
The present work aims to address the electronic and magnetic properties of the intermetallic compound GdPd$_2$Bi through a comprehensive study of the structural, magnetic, electrical and thermal transport on a polycrystalline sample, followed by theoretical calculations. Our findings indicate that the magnetic ground state is antiferromagnetic in nature. Magnetotransport data present prominent hysteresis loop hinting a structural transition with further support from specific heat and thermopower measurements, but no such signature is observed in the magnetization study. Temperature dependent p…
Pd$_{3}$Bi$_{2}$Se$_{2}$ has been proposed to be topologically non-trivial in nature. However, evidence of its non-trivial behavior is still unexplored. We report the growth and magneto-transport study of Pd$_{3}$Bi$_{2}$Se$_{2}$ thin films, revealing for the first time the contribution of two-dimensional (2D) topological surface states. We observe exceptional non-saturated linear magnetoresistance which results from Dirac fermions inhabiting the lowest Landau level in the quantum limit. The transverse magnetoresistance changes from a semi-classical weak-field $B^{2}$ dependence to a high-fiel…
Quantum oscillations with non-zero Berry phase from a complex three dimensional Fermi surface in Bi2Te3
我们进行了角度相关的磁电阻研究的金属单晶样品的Bi 2 Te 3。我们发现当磁场与样品平面垂直方向成小角度时，样品的磁电阻在正、负磁场中是高度不对称的。当角度接近90度时，磁阻变得对称。量子Shubnikov de-Haas振荡是对称的，并且显示出具有非零Berry相位形式的Dirac色散的拓扑表面态的特征。然而，这些振荡的角度依赖性表明一个复杂的三维费米面作为这些振荡的源，这并不完全符合六椭球模型的费米面的Bi 2 Te 3。我们将磁阻的不对称性归因于纵向电阻中的霍尔电压的混合，这是由于我们的样品中的霍尔和纵向电阻的幅度相当。这为理解这种材料和类似材料中常见的非对称磁阻提供了线索。此外，不对称性质随着暴露于大气和热循环而演变，我们认为这是由于暴露于大气或热循环，或者两者都影响载流子浓度，从而影响这些样品中的霍尔信号。然而，量子振荡似乎对这些因素具有鲁棒性，这表明两者具有不同的起源。
