A large negative magnetoresistance (NMR) is anticipated in topological semimetals in parallel magnetic fields, demonstrating the chiral anomaly, a long-sought high-energy-physics effect, in solid-state systems. Recent experiments reveal that the Dirac semimetal Cd3As2 has the record-high mobility and positive linear magnetoresistance in perpendicular magnetic fields. However, the NMR has not yet been unveiled. Here we report the observation of NMR in Cd3As2 microribbons in parallel magnetic fields up to 66% at 50 K and visible at room temperatures. The NMR is sensitive to the angle between magnetic and electrical fields, robust against temperature and dependent on the carrier density. The large NMR results from low carrier densities in our Cd3As2 samples, ranging from 3.0 × 1017 cm−3 at 300 K to 2.2 × 1016 cm−3 below 50 K. We therefore attribute the observed NMR to the chiral anomaly. In perpendicular magnetic fields, a positive linear magnetoresistance up to 1,670% at 14 T and 2 K is also observed.

In Central Asia, thrusts and shear zones resulting from Palaeozoic accretional events were reworked by E–W‐trending ductile strike‐slip faults during late Palaeozoic–early Mesozoic time. In the Tianshan range, microstructures and quartz C‐axis fabrics show a main dextral shearing associated with sinistral localized shear zones. The relationship between these conjugate structures indicates a NNW–SSE‐trending bulk shortening. In the Chinese Altay mountains, the existence of δ‐type microstructures in an important sinistral mylonitic zone infers high rates of deformation. This shear zone is bordered by a late dextral ductile fault synchronous with a granite emplacement. Field evidence and datings from the literature provide chronological constraints. In the late Carboniferous, the sinistral mylonitic deformation took place in the Erqishi–Irtysh shear zone in the northeastern part of Xinjiang and in Kazakhstan. During the Early Permian, a regional dextral event occurred in the Tianshan range and under the whole of northern Xinjiang.

Revealing the active phase and structure of catalyst nanoparticles (NPs) is crucial for understanding the growth mechanism and realizing the controlled synthesis of carbon nanotubes (CNTs). However, due to the high temperature and complex environment during CNT growth, precise identification of the active catalytic phase remains a great challenge. We investigated the phase evolution of cobalt (Co) catalyst NPs during the incubation, nucleation, and growth stages of CNTs under near-atmospheric pressure using an in situ close-cell environmental transmission electron microscope (ETEM). Strict statistical analysis of the electron diffractograms was performed to accurately identify the phases of the catalyst NPs. It was found that the NPs belong to an orthorhombic Co 3 C phase that remained unchanged during CNT growth, with errors in lattice spacing <5% and in angle <2°, despite changes in their morphology and orientation. Theoretical calculations further confirm that Co 3 C is the thermodynamically preferred phase during CNT growth, with the supply of carbon atoms through the surface and NP−CNT interfacial diffusion.

Weyl semimetals (WSMs) host charged Weyl fermions as emergent quasiparticles. We develop a unified analytical theory for the anomalous positive longitudinal magnetoconductance (LMC) in a WSM, which bridges the gap between the classical and ultra-quantum approaches. More interestingly, the LMC is found to exhibit periodic-in-1/B quantum oscillations, originating from the oscillations of the nonequilibrium chiral chemical potential. The quantum oscillations, superposed on the positive LMC, are a remarkable fingerprint of a WSM phase with chiral anomaly, whose observation is a valid criteria for identifying a WSM material. In fact, such quantum oscillations were already observed by several experiments.Weyl semimetals (WSMs), whose low-energy excitations are Weyl fermions [1] carrying charges, have recently spurred intensive and innovative research in the field of condensed matter physics [2][3][4][5][6][7][8]. The ultrahigh mobility and spectacular transport properties of the charged Weyl fermions can find applications in highspeed electronic circuits and computors [9][10][11]. The lowenergy spectrum of a WSM forms non-degenerate threedimensional (3D) Dirac cones around isolated degenerate band touching points, referred to as Weyl points [2]. Weyl points with opposite chiralities, playing the parts of the source and sink of Berry curvature in momentum space, always come in pairs [12,13]. The appearance of the Weyl points requires breaking either the spatial inversion or time-reversal symmetry. Weyl points with opposite chiralities in momentum space are connected by the nonclosed Fermi arc surface states [2].The WSM state was first realized experimentally in TaAs [14-16], following the theoretical predictions [17,18], and later in several different compounds [10,[19][20][21][22][23][24][25][26][27][28][29]. WSMs display many anomalous transport properties, such as positive longitudinal magnetoconductance (LMC), optical gyrotropy [30], planar Hall effect [31], all of which are induced by the chiral anomaly [13], and nonlocal quantum oscillations of the Fermi arc surface states [32]. The chiral anomaly, also termed as the Adler-Bell-Jackiw anomaly, means the violation of the separate number conservation laws of Weyl fermions of different chiralities. Parallel electric and magnetic fields can pump Weyl fermions between Weyl valleys of opposite chiralities, and create a population imbalance between them, therefore resulting in a positive LMC (or negative magne- * shengli@nju.edu.cn † dyx@nju.edu.cn toresistance). The anomalous LMC, as an exotic macroscopic quantum phenomenon, has been attracting intense experimental [10,[20][21][22][23][24][25][26][27][28][29] and theoretical [7,[33][34][35][36] interest.In order to identify a WSM material, the ARPES experiments were used to directly observe the Weyl nodes and Fermi arcs [14][15][16]19]. However, the ARPES identification is sometime limited by spectroscopic resolutions. Another widely-employed method is to measure the positive LMC induced by the chiral anomaly [10,[20][2...

We numerically study the thermoelectric transports of Dirac fermions in graphene in the presence of a strong magnetic field and disorder. We find that the thermoelectric transport coefficients demonstrate universal behavior depending on the ratio between the temperature and the width of the disorder-broadened Landau levels (LLs). The transverse thermoelectric conductivity alpha{xy} reaches a universal quantum value at the center of each LL in the high temperature regime, and it has a linear temperature dependence at low temperatures. The calculated Nernst signal has a peak at the central LL with heights of the order of k{B}/e, and changes sign near other LLs, while the thermopower has an opposite behavior, in good agreement with experimental data. The validity of the generalized Mott relation between the thermoelectric and electrical transport coefficients is verified in a wide range of temperatures.

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