Ultrahigh mobility and giant magnetoresistance in the Dirac semimetal Cd$_3$As$_2$

TL;DR

This study reveals that Cd$_3$As$_2$, a Dirac semimetal, exhibits ultrahigh electron mobility and giant linear magnetoresistance due to a unique back-scattering suppression mechanism, with magnetic fields disrupting this protection.

Contribution

The paper uncovers a novel back-scattering protection mechanism in Cd$_3$As$_2$ that results in ultrahigh mobility and giant magnetoresistance, expanding understanding of transport in Dirac semimetals.

Findings

Electron mobility exceeds 10^7 cm^2/Vs below 4 K.

Back-scattering suppression leads to a transport lifetime 10^4 times longer than quantum lifetime.

Magnetic field lifts the protection, causing giant linear magnetoresistance.

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 $\bf H$.