The chiral magnetic effect is the generation of electric current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum anomaly 1,2 in rel-ativistic field theory of chiral fermions (massless spin 1/2 particles with a definite projection of spin on momentum)-a dramatic phenomenon arising from a collective motion of particles and antiparti-cles in the Dirac sea. The recent discovery 3-5 of Dirac semimetals with chiral quasi-particles opens a fascinating possibility to study this phenomenon in condensed matter experiments. Here we report on the first observation of chiral magnetic effect through the measurement of magneto-transport in zirconium pentatelluride, ZrTe 5. Our angle-resolved photoemission spectroscopy experiments show that this material's electronic structure is consistent with a 3D Dirac semimetal. We observe a large negative magnetoresistance when magnetic field is parallel with the current. The measured quadratic field dependence of the magnetoconductance is a clear indication of the chiral magnetic effect. The observed phenomenon stems from the effective transmutation of Dirac semimetal into a Weyl semimetal induced by the parallel electric and magnetic fields that represent a topologically nontrivial gauge field background.
Resistivity measurements have been performed as a function of temperature (1–300 K) and magnetic field (0–10 T) on antiferromagnetically coupled Fe-Cr-Fe sandwiches. Two types of samples were studied: MBE-grown sandwiches deposited epitaxially on the ZnSe (100) surface, and evaporated polycrystalline sandwiches deposited on glass substrates. The magnetic saturation field Hs determined from the resistivity ρ(H,T) is linear with temperature throughout the full temperature range for all samples. In the polycrystalline sandwiches, where the observed in-plane magnetic anisotropy is small, the linearity of Hs(T) implies that the antiferromagnetic interlayer exchange coupling A12 is also linear with temperature. The magnetoresistance of the sandwiches is constant at low temperature, and decreases linearly with increasing temperature above about 70 K.
%e present a study of charge-density-wave metastable states below 4.2 K in thermally quenched NbSe3. These states and their ensuing relaxation are manifest most strongly in the Shubnikov-de Haas (SdH) oscillations. The quenched metastable state remains without any change for time scales ranging from several minutes to several hours before a sharp relaxation is observed. Sharp jumps in the magnetoresistance and the amplitudes of the SdH oscillations are observed when the metastable states relax spontaneously. %'e present evidence that these relaxations are not driven by the magnetic field, H, the current, or a combination of the two. The SdH oscillation frequencies with H parallel to c indicate a 12% decrease in the extremal area of the conduction-electron Fermi surface after relaxation to the equilibrium state. However, the determination of the Hall coefhcient suggests that this change is not simply related to a change in the carrier concentration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.