Ultrahigh mobility and giant magnetoresistance in the Dirac semimetal Cd\(_3\)As\(_2\)

Abstract

Dirac semimetals and Weyl semimetals are 3D analogs of graphene in which crystalline symmetry protects the nodes against gap formation [1-3]. Na\(_3\)Bi and Cd\(_3\)As\(_2\) were predicted to be Dirac semimetals [4,5], and recently confirmed to be so by photoemission [6-8]. Several novel transport properties in a magnetic field \(\bf H\) have been proposed for Dirac semimetals [2,9-11]. Here we report an interesting property in Cd\(_3\)As\(_2\) that was unpredicted, namely a remarkable protection mechanism that strongly suppresses back-scattering in zero \(\bf H\). In single crystals, the protection results in a very high mobility that exceeds \(>10^7\) cm\(^2\)/Vs below 4 K. Suppression of backscattering results in a transport lifetime 10\(^4\times\) longer than the quantum lifetime. The lifting of this protection by \(\bf H\) leads to an unusual giant \(\bf H\)-linear magnetoresistance that violates Kohler's rule. We discuss how this may relate to changes to the Fermi surface induced by \(\bf H\).