Nonlocal signatures of the chiral magnetic effect in the Dirac semimetal Bi0.97Sb0.03

Abstract

The field of topological materials science has recently been focussing on three-dimensional Dirac semimetals, which exhibit robust Dirac phases in the bulk. However, the absence of characteristic surface states in accidental Dirac semimetals (DSM) makes it difficult to experimentally verify claims about the topological nature using commonly used surface-sensitive techniques. The chiral magnetic effect (CME), which originates from the Weyl nodes, causes an E · B-dependent chiral charge polarization, which manifests itself as negative magnetoresistance. We exploit the extended lifetime of the chirally polarized charge and study the CME through both local and non-local measurements in Hall bar structures fabricated from single crystalline flakes of the DSM Bi0.97Sb0.03. From the non-local measurement results we find a chiral charge relaxation time which is over one order of magnitude larger than the Drude transport lifetime, underlining the topological nature of Bi0.97Sb0.03.

Weak antilocalization, spin–orbit interaction, and phase coherence length of a Dirac semimetal Bi0.97Sb0.03

“…Here, a negative slope at high temperatures corresponds to an insulating-like region and a positive slope at low temperatures is a metallic-like region. Such behavior is driven by B , which is consistent with previous literature 18 . Possibly, this observation suggests a certain role of Landau level formation particularly at low T , but the origin of this transition-like behavior is still elusive.…”

Room-temperature valley transistors for low-power neuromorphic computing

“…The simulation results suggest that the signal from conventional charge diffusion (Ohmic contribution) is negligible due to its short mean free path of electrons (e.g. tens of nm in Si), consistent with the previous non-local chiral anomaly work 13 . These length-, width-and carrier-density-dependent results reveal the presence of low-loss valley transport based on the chiral anomaly in the Te samples.…”

“…We can control valley transport by modulating Berry curvature, which determines the pumping rate (w) of imbalanced valley according to Eq. (1) 13,22 :…”

“…Chiral anomaly in Weyl/Dirac materials allows to generate valley polarization that can diffuse over a long distance (~100 μm in theory) and sustain under thermal perturbation 12 , providing an alternative mechanism for room-temperature valley transistors (Supplementary Note 1). By applying an electric field that is parallel to the magnetic field, the valley polarization generated by the chiral anomaly can transport over a long distance at room temperature, because the relaxation process involves a large quasimomentum transfer [12][13][14] . As the chiral anomaly-based valley transport arises from the non-trivial Berry curvature, we can realize valley transistors by modulating the strength of Berry curvature through the electrostatic gating at room temperature.…”

Chiral Magnetic Effect of Hot Electrons

“…Therefore, the resultant signals are even in the magnetic field. While it is still possible to measure them [21][22][23], great care must be taken to distinguish the topology-related effects from mundane Ohmic physics [22,24] In this Letter, we present a new way to observe the chiral magnetic effect in non-centrosymmetric Weyl semimetals under the action of strong electric fields, via the non-linear part of the I-V characteristic that is odd in the external magnetic field. In this approach, the chiral imbalance is generated by valley-dependent heating which occurs either due to anisotropy of a crystal [25], or its gyrotropy.…”