Fermi surface topology and negative longitudinal magnetoresistance observed in centrosymmetric NbAs2 semimetal
Bing Shen, Xiaoyu Deng, Gabriel Kotliar, Ni Ni
备注：
5 pages. Some content from the previous version has been removed so that the paper is more focused on SdH quantum oscillations and negative longitudinal magentoresistance
We report transverse and longitudinal magneto-transport properties of NbAs2 single crystals. Attributing to the electron-hole compensation, non-saturating large transverse magnetoresistance reaches up to 8000 at 9 T at 1.8 K with mobility around 1 to 2 m^2V^-1S^-1. We present a thorough study of angular-dependent Shubnikov-de Haas (SdH) quantum oscillations of NbAs2. Three distinct oscillation frequencies are identified. First-principles calculations reveal four types of Fermi pockets: electron alpha pocket, hole beta pocket, hole gamma pocket and small electron delta pocket. Although the angular dependence of alpha, beta and delta agree well with the SdH data, it is unclear why the gamma pocket is missing in SdH. Negative longitudinal magnetoresistance is observed which may be linked to novel topological states in this material, although systematic study is necessary to ascertain its origin.
We performed a systematic study of the temperature- and field-dependence of magnetization and resistivity of Gd2PdSi3, which is a centrosymmetric skyrmion crystal. While the magnetization behavior is consistent with the reported phase diagram based on susceptibility, we show that a phase diagram can also be constructed based on the anomalous magnetoresistance with one-to-one correspondence among all the features. In addition, the crossover boundary into the field-induced ferromagnetic state is also identified. Our results suggest that the ferromagnetic spin fluctuations above the Néel temperat…
The transverse and longitudinal magnetoresistance (MR) of two samples of the topological chiral semimetal CoSi with different RRR was studied. It is shown that the Kohler rule works for the transverse MR. The Kohler rule is also fulfilled in the case of longitudinal MR at a low reduced magnetic field. A sharp deviation of longitudinal MR curve for sample with low RRR from the Kohler prediction at high fields reveals its tendency to a sign change at higher magnetic fields. The Shubnikov de Haas quantum oscillations were observed and analyzed in both perpendicular and parallel configurations of …
Incommensurate magnetic order drives singular angular magnetoresistance in a Weyl semimetal
Boston College（波士顿学院）；NIST Center for Neutron Research, National Institute of Standards and Technology（美国国家标准与技术研究院中子研究中心）；Tata Institute of Fundamental Research（塔塔基础研究所）；University of California, Los Angeles（加州大学洛杉矶分校）；Oak Ridge National Laboratory（橡树岭国家实验室）；National Synchrotron Radiation Research Center（国家同步辐射研究中心）；ISIS neutron and muon source, STFC, Rutherford Appleton Laboratory（STFC卢瑟福阿普尔顿实验室ISIS中子和缪子源）；J-PARC Center, Japan Atomic Energy Agency（日本原子能机构J-PARC中心）；University of Tsukuba（筑波大学）
We report the effect of Dirac cone tilting on interlayer magnetoresistance in α-(BEDT-TTF)$_2$I$_3$, which is a Dirac semimetal under pressure. Fitting of the experimental data by the theoretical formula suggests that the system is close to a type-II Dirac semimetal.
Spin-charge conversion via spin-orbit interaction is one of the core concepts in the current spintronics research. The efficiency of the interconversion between charge and spin current is estimated based on Berry curvature of Bloch wavefunction in the linear-response regime. Beyond the linear regime, nonlinear spin-charge conversion in the higher-order electric field terms has recently been demonstrated in noncentrosymmetric materials with nontrivial spin texture in the momentum space. Here we report the observation of the nonlinear charge-spin conversion in a nominally centrosymmetric oxide m…
The non-centrosymmetric Weyl semimetal candidate, MoTe$_2$ was investigated through neutron diffraction and transport measurements at pressures up to 1.5 GPa and at temperatures down to 40 mK. Centrosymmetric and non-centrosymmetric structural phases were found to coexist in the superconducting state. Density Functional Theory (DFT) calculations reveal that the strength of the electron-phonon coupling is similar for both crystal structures. Furthermore, it was found that by controlling non-hydrostatic components of stress, it is possible to mechanically control the ground state crystal structu…
In this work we report the results of DC susceptibility, AC susceptibility and related technique, resistivity, transverse and longitudinal magnetoresistance and heat capacity on polycrystalline magnetic semimetal CeAlGe. This compound undergoes antiferromagnetic type ordering around 5.2 K (T1). Under application of external magnetic fields, parallel alignment of magnetic moments is favored, above 0.5 Tesla. At low field and temperature, frequency and AC field amplitude response of AC susceptibility indicate to the presence of spin-lattice relaxation phenomena. The observation of spin-lattice i…
Extremely large magnetoresistance (XMR) was recently discovered in many non-magnetic materials, while its underlying mechanism remains poorly understood due to the complex electronic structure of these materials. Here, we report an investigation of the $α$-phase WP$_2$, a topologically trivial semimetal with monoclinic crystal structure (C2/m), which contrasts to the recently discovered robust type-II Weyl semimetal phase in $β$-WP$_2$. We found that $α$-WP$_2$ exhibits almost all the characteristics of XMR materials: the near-quadratic field dependence of MR, a field-induced up-turn in resist…
We performed calculations of the electronic band structure and the Fermi surface as well as measured the longitudinal resistivity $ρ_{xx}(T,H)$, Hall resistivity $ρ_{xy}(T,H)$, and magnetic susceptibility as a function of temperature and various magnetic fields for VAs$_2$ with a monoclinic crystal structure. The band structure calculations show that VAs$_2$ is a nodal-line semimetal when spin-orbit coupling is ignored. The emergence of a minimum at around 11 K in $ρ_{xx}(T)$ measured at $H$ = 0 demonstrates that an additional magnetic impurity (V$^{4+}$, $S$ = 1/2) occurs in VAs$_2$ single cr…
SrIrO3, the three-dimensional member of the Ruddlesden-Popper iridates, is a paramagnetic semimetal characterised by a the delicate interplay between spin-orbit coupling and Coulomb repulsion. In this work, we study the anisotropic magnetoresistance (AMR) of SrIrO3 thin films, which is closely linked to spin-orbit coupling and probes correlations between electronic transport, magnetic order and orbital states. We show that the low-temperature negative magnetoresistance is anisotropic with respect to the magnetic field orientation, and its angular dependence reveals the appearance of a fourfold…
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…
We present a study of Cu-substitution effects in 4f-Ce intermetallic compound CeAu1-xCuxGe, with potentially unusual electronic states, in the whole concentration range (x = 0.0 - 1.0). The parent CeAuGe compound, crystallizing in a non-centrosymmetric hexagonal structure, is a ferromagnetic semimetal with Curie temperature 10 K. Cu-doping on Au-site of CeAuGe, CeAu1-xCuxGe, changes the crystal structure from the non-centrosymmetric (P63mc) to centrosymmetric (P63/mmc) space group at the concentration x ~ 0.5, where the c-lattice constant has a maximum value. Magnetic susceptibility and electr…
Extremely large positive magnetoresistance (XMR) was found in a nonmagnetic semimetal InBi. Using several single crystals with different residual resistivity ratios (RRRs), we revealed that the XMR strongly depended on the RRR (sample quality). Assuming that there were no changes in effective mass m* and carrier concentrations in these single crystals, this dependence was explained by a semiclassical two-carrier model. First-principle calculations including the spin-orbit interactions (SOI) unveiled that InBi had a compensated carrier balance and SOI-induced "hidden" three-dimensional (3D) Dir…
We present a theory of thermoelectric transport in weakly disordered Weyl semimetals where the electron-electron scattering time is faster than the electron-impurity scattering time. Our hydrodynamic theory consists of relativistic fluids at each Weyl node, coupled together by perturbatively small inter-valley scattering, and long-range Coulomb interactions. The conductivity matrix of our theory is Onsager reciprocal and positive-semidefinite. In addition to the usual axial anomaly, we account for the effects of a distinct, axial-gravitational anomaly expected to be present in Weyl semimetals.…
Weyl semimetals such as the TaAs family (TaAs, TaP, NbAs, NbP) host quasiparticle excitations resembling the long sought after Weyl fermions at special band-crossing points in the band structure denoted as Weyl nodes. They are predicted to exhibit a negative longitudinal magnetoresistance (LMR) due to the chiral anomaly if the Fermi energy is sufficiently close to the Weyl points. However, current jetting effects, i.e. current inhomogeneities caused by a strong, field-induced conductivity anisotropy in semimetals, have a similar experimental signature and therefore have hindered a determinatio…
Weyl semimetal with Weyl fermions at Fermi energy is one of the topological materials, and is a condensed-matter realization of the relativistic fermions. However, there are several crucial differences such as the shift of Fermi energy, which can hinder the expected interesting physics. Chiral anomaly is a representative nontrivial phenomenon associated with Weyl fermions, which dictates the transfer of fermions between the Weyl fermions with opposite chirality; it is manifested as the negative magnetoresistance. Here we demonstrate that the magnetoresistance is robust against the deviation fr…
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…
In the Dirac/Weyl semimetal, the chiral anomaly appears as an "axial" current arising from charge-pumping between the lowest (chiral) Landau levels of the Weyl nodes, when an electric field is applied parallel to a magnetic field $\bf B$. Evidence for the chiral anomaly was obtained from the longitudinal magnetoresistance (LMR) in Na$_3$Bi and GdPtBi. However, current jetting effects (focussing of the current density $\bf J$) have raised general concerns about LMR experiments. Here we implement a litmus test that allows the intrinsic LMR in Na$_3$Bi and GdPtBi to be sharply distinguished from …
Magnetoresistance in Magnetic Weyl semimetal Mn$_{3}$ZnC
School of Physical Sciences, Indian Institute of Technology Mandi（印度技术学院曼迪分校物理科学学院）；Center for Quantum Science and Technologies, Indian Institute of Technology Mandi（印度技术学院曼迪分校量子科学与技术中心）
A number of rare-earth monopnictides have topologically non-trivial band structures together with magnetism and strong electronic correlations. In order to examine whether the antiferromagnetic (AFM) semimetal YbAs ($T\rm_N$ = 0.5 K) exhibits such a scenario, we have grown high-quality single crystals using a flux method, and characterized the magnetic properties and electronic structure using specific heat, magnetotransport and angle-resolved photoemission spectroscopy (ARPES) measurements, together with density functional theory (DFT) calculations. Both ARPES and DFT calculations find no evi…
The discovery of non-magnetic extreme magnetoresistance (XMR) materials has induced great interests because the XMR phenomenon challenges our understanding of how a magnetic field can alter electron transport in semimetals. Among XMR materials, the LaSb shows XMR and field-induced exotic behaviors but it seems to lack the essentials for these properties. Here, we study the magnetotransport properties and electronic structure of LaBi, isostructural to LaSb. LaBi exhibits large MR as in LaSb, which can be ascribed to the nearly compensated electron and hole with rather high mobilities. More impo…
The behavior of charge density wave (CDW) in an external magnetic field is dictated by both orbital and Pauli (Zeeman) effects. A quasi-one-dimensional (Q1D) system features Q1D Fermi surfaces that allow these effects to be distinguished, which in turn can provide sensitive probe to the underlying electronic states. Here we studied the field dependence of an incommensurate CDW in a transition-metal chalcogenide Ta2NiSe7 with a Q1D chain structure. The angle-dependent magnetoresistance (MR) is found to be very sensitive to the relative orientation between the magnetic field and the chain direct…
The unusual features of topological semimetals arise from its nontrivial band structure. The impact of strong electron correlations on the topological states remains largely unexplored in real materials. Here, we report the magnetotransport properties of YbCdSn single crystals. We found two fundamental experimental evidences of electron correlations through magnetic susceptibility and specific heat. The electron correlations in this compound lead to an intermediate valence state and enhance the effective mass of the charge carriers. This correlated state exhibits large nonsaturating magnetores…
Recent experiments on type-II Weyl semimetals such as WTe$_2$, MoTe$_2$, Mo$_x$W$_{1-x}$Te$_2$ and WP$_2$ reveal remarkable transport properties in presence of a strong magnetic field, including an extremely large magnetoresistance and an unusual temperature dependence. Here, we investigate magnetotransport via the Kubo formula in a minimal model of a type-II Weyl semimetal taking into account the effect of a charge density wave (CDW) transition, which can arise even at weak coupling in the presence of a strong magnetic field because of the special Landau level dispersion of type-II Weyl syste…
Weyl semimetals, characterized by nodal points in the bulk and Fermi arc states on the surface, have recently attracted extensive attention due to the potential application on low energy consumption electronic materials. In this report, the thermodynamic and transport properties of a theoretically predicted Weyl semimetal NbIrTe4 is measured in high magnetic fields up to 35 T and low temperatures down to 0.4 K. Remarkably, NbIrTe4 exhibits a nonsaturating transverse magnetoresistance which follows a power-law dependence in B. Low-field Hall measurements reveal that hole-like carriers dominate …
Negative magnetoresistance (NMR) induced by the Adler-Bell-Jackiw anomaly is regarded as the most prominent quantum signature of Weyl semimetals when electrical field $E$ is collinear with the external magnetic field $B$. In this article, we report universal NMR in nonmagnetic, centrosymmetric transition metal dipnictides MPn$_{2}$ (M=Nb and Ta; Pn=As and Sb), in which the existence of Weyl fermions can be explicitly excluded. Using temperature-dependent magnetoresistance, Hall and thermoelectric coefficients of Nernst and Seebeck effects, we determine that the emergence of the NMR phenomena i…
The combination of magnetic symmetries and electronic band topology provides a promising route for realizing topologically nontrivial quasiparticles, and the manipulation of magnetic structures may enable the switching between topological phases, with the potential for achieving functional physical properties. Here, we report measurements of the electrical resistivity of EuCd$_2$As$_2$ under pressure, which show an intriguing insulating dome at pressures between $p_{\rm c1}\sim1.0$~GPa and $p_{\rm c2}\sim2.0$~GPa, situated between two regimes with metallic transport. The insulating state can b…
We instigate the angle-dependent magnetoresistance (AMR) of the layered nodal-line Dirac semimetal ZrSiS for the in-plane and out-of-plane current directions. This material has recently revealed an intriguing butterfly-shaped in-plane AMR that is not well understood. Our measurements of the polar out-of-plane AMR show a surprisingly different response with a pronounced cusp-like feature. The maximum of the cusp-like anisotropy is reached when the magnetic field is oriented in the $a$-$b$ plane. Moreover, the AMR for the azimuthal out-of-plane current direction exhibits a very strong four-fold …
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 …
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…
While recent advances in band theory and sample growth have expanded the series of extremely large magnetoresistance (XMR) semimetals in transition metal dipnictides $TmPn_2$ ($Tm$ = Ta, Nb; $Pn$ = P, As, Sb), the experimental study on their electronic structure and the origin of XMR is still absent. Here, using angle-resolved photoemission spectroscopy combined with first-principles calculations and magnetotransport measurements, we performed a comprehensive investigation on MoAs$_2$, which is isostructural to the $TmPn_2$ family and also exhibits quadratic XMR. We resolve a clear band struct…
The resistance of a metal in a magnetic field can be very illuminating about its ground state. Some famous examples include the integer and fractional quantum Hall effects\cite{Klitzing-QHE,Tsui-FQHE}, Shubnikov-de Haas oscillations\cite{SdH}, and weak localization\cite{Lee-WL} \emph{et al}. In non-interacting metals the resistance typically increases upon the application of a magnetic field\cite{Pippard-MR}. In contrast, in some special circumstances metals, with anisotropic Fermi surfaces\cite{Kikugawa-PdCoO2LMR} or a so-called Weyl semimetal for instance\cite{Nielsen-ABJ,Son-ChirAnom}, may …
Two-component conductors -- e.g., semi-metals and narrow band semiconductors -- often exhibit unusually strong magnetoresistance in a wide temperature range. Suppression of the Hall voltage near charge neutrality in such systems gives rise to a strong quasiparticle drift in the direction perpendicular to the electric current and magnetic field. This drift is responsible for a strong geometrical increase of resistance even in weak magnetic fields. Combining the Boltzmann kinetic equation with sample electrostatics, we develop a microscopic theory of magnetotransport in two and three spatial dim…
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=(sin2θ+γ-2cos2θ)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 characte…
We report a detailed magneto-transport study in single crystals of NbP. High quality crystals were grown by vapour transport method. An exceptionally large magnetoresistance is confirmed at low temperature which is non-saturating and is linear at high fields. Models explaining the linear magnetoresistance are discussed and it is argued that in NbP this is linked to charge carrier mobility fluctuations. Negative longitudinal magnetoresistance is not seen, unlike several other Weyl monopnictides, suggesting lack of well defined chiral anomaly in NbP. Unambiguous Shubnikov-de-Haas oscillations ar…
We report a comprehensive investigation of the structural, magnetic, transport and thermodynamic properties of a single crystal PrAlSi, in comparison to its nonmagnetic analogue LaAlSi. PrAlSi exhibits a ferromagnetic transition at $T_C$ = 17.8 K which, however, is followed by two weak phase transitions at lower temperatures. Based on the combined dc and ac magnetic susceptibility measurements, we propose the two reentrant magnetic phases below $T_C$ to be spin glasses or ferromagnetic cluster glasses. When the magnetic glassy states are suppressed by small field, several remarkable features a…
We report the first experimental results of the magnetoresistance, Hall effect, and quantum Shubnikov-de Haas oscillations on single crystals of ZrTe, which was recently predicted to be a new type of topological semimetal hosting both triply degenerate crossing points and Weyl fermion state. The analysis of Hall effect and quantum oscillations indicate that ZrTe is a multiband system with low carrier density, high carrier mobility, small cross-sectional area of Fermi surface, and light cyclotron effective mass, as observed in many topological semimetals. Meanwhile, the angular dependence of th…
The acute sensitivity of the electrical resistance of certain systems to magnetic fields known as extreme magnetoresistance (XMR) has recently been explored in a new materials context with topological semimetals. Exemplified by WTe$_{2}$ and rare earth monopnictide La(Sb,Bi), these systems tend to be non-magnetic, nearly compensated semimetals and represent a platform for large magnetoresistance driven by intrinsic electronic structure. Here we explore electronic transport in magnetic members of the latter family of semimetals and find that XMR is strongly modulated by magnetic order. In parti…
The newly discovered topological Dirac semimetals host the possibilities of various topological phase transitions through the control of spin-orbit coupling as well as symmetries and dimensionalities. Here, we report a magnetotransport study of high-mobility (Cd1-xZnx)3As2 films, where the topological Dirac semimetal phase can be turned into a trivial insulator via chemical substitution. By high-field measurements with a Hall-bar geometry, magnetoresistance components ascribed to the chiral charge pumping have been distinguished from other extrinsic effects. The negative magnetoresistance exhi…
A notable phenomenon in topological semimetals is the violation of Kohler$^,$s rule, which dictates that the magnetoresistance $MR$ obeys a scaling behavior of $MR = f(H/ρ_0$), where $MR = [ρ_H-ρ_0]/ρ_0$ and $H$ is the magnetic field, with $ρ_H$ and $ρ_0$ being the resistivity at $H$ and zero field, respectively. Here we report a violation originating from thermally-induced change in the carrier density. We find that the magnetoresistance of the Weyl semimetal, TaP, follows an extended Kohler$^,$s rule $MR = f[H/(n_Tρ_0)]$, with $n_T$ describing the temperature dependence of the carrier densit…
We introduce a simple model to describe the formation of heavy Weyl semimetals in non-centrosymmetric heavy fermion compounds under the influence of a parity-mixing, onsite hybridization. A key aspect of interaction-driven heavy Weyl semimetals is the development of surface Kondo breakdown, which is expected to give rise to a temperature-dependent re-configuration of the Fermi arcs and the Weyl cyclotron orbits which connect them via the chiral bulk states. Our theory predicts a strong temperature dependent transformation in the quantum oscillations at low temperatures. In addition to the effe…
Topological Semimetal Transport Modulated by Interstitial Fe in Ba(Fe$_{1-x}$Co$_x$)$_{2+δ}As$_2$ Superconductors
Tsinghua University（清华大学）；Renmin University of China（中国人民大学）；Southern University of Science and Technology（南方科技大学）；Huazhong University of Science and Technology（华中科技大学）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Hefei National Laboratory（合肥国家实验室）
