Extreme magnetoresistance in the topologically trivial lanthanum monopnictide LaAs

TL;DR

This study investigates LaAs, a topologically trivial lanthanum monopnictide, revealing that compensation between electron and hole densities, rather than topological effects, primarily drives its extreme magnetoresistance, with mobility mismatch limiting its magnitude.

Contribution

The paper demonstrates that LaAs exhibits XMR without topological features, emphasizing the role of electron-hole compensation and mobility mismatch in XMR magnitude.

Findings

LaAs shows XMR similar to LaSb and LaBi but with lower magnitude.

Absence of band inversion indicates topology is not essential for XMR.

Electron-hole compensation correlates with XMR, but mobility mismatch constrains its size.

Abstract

The family of binary Lanthanum monopnictides, LaBi and LaSb, have attracted a great deal of attention as they display an unusual extreme magnetoresistance (XMR) that is not well understood. Two classes of explanations have been raised for this: the presence of non-trivial topology, and the compensation between electron and hole densities. Here, by synthesizing a new member of the family, LaAs, and performing transport measurements, Angle Resolved Photoemission Spectroscopy (ARPES), and Density Functional Theory (DFT) calculations, we show that (a) LaAs retains all qualitative features characteristic of the XMR effect but with a siginificant reduction in magnitude compared to LaSb and LaBi, (b) the absence of a band inversion or a Dirac cone in LaAs indicates that topology is insignificant to XMR, (c) the equal number of electron and hole carriers indicates that compensation is necessary for XMR but does not explain its magnitude, and (d) the ratio of electron and hole mobilities is much different in LaAs compared to LaSb and LaBi. We argue that the compensation is responsible for the XMR profile and the mobility mismatch constrains the magnitude of XMR.