Separation of Electron and Hole Dynamics in the Semimetal LaSb

TL;DR

This study investigates the electron and hole dynamics in LaSb, revealing that its extremely large magnetoresistance arises from high mobility and multi-band effects, without requiring topological protection, and introduces a method to distinguish charge carrier contributions.

Contribution

The paper presents a new approach to separate electron and hole contributions to magnetoresistance in multi-band materials with anisotropic Fermi surfaces, applicable to other XMR materials.

Findings

Resistivity plateau explained without topological protection.

Good agreement between Fermi surface measurements and calculations.

High mobility and multi-band effects cause XMR in LaSb.

Abstract

We report investigations on the magnetotransport in LaSb, which exhibits extremely large magnetoresistance (XMR). Foremost, we demonstrate that the resistivity plateau can be explained without invoking topological protection. We then determine the Fermi surface from Shubnikov - de Haas (SdH) quantum oscillation measurements and find good agreement with the bulk Fermi pockets derived from first principle calculations. Using a semiclassical theory and the experimentally determined Fermi pocket anisotropies, we quantitatively describe the orbital magnetoresistance, including its angle dependence. We show that the origin of XMR in LaSb lies in its high mobility with diminishing Hall effect, where the high mobility leads to a strong magnetic field dependence of the longitudinal magnetoconductance. Unlike a one-band material, when a system has two or more bands (Fermi pockets) with electron and hole carriers, the added conductance arising from the Hall effect is reduced, hence revealing the latent XMR enabled by the longitudinal magnetoconductance. With diminishing Hall effect, the magnetoresistivity is simply the inverse of the longitudinal magnetoconductivity, enabling the differentiation of the electron and hole contributions to the XMR, which varies with the strength and orientation of the magnetic field. This work demonstrates a convenient way to separate the dynamics of the charge carriers and to uncover the origin of XMR in multi-band materials with anisotropic Fermi surfaces. Our approach can be readily applied to other XMR materials.