Perfect charge compensation in extremely large magnetoresistance materials LaSb and LaBi revealed by the first-principles calculations

TL;DR

This study uses first-principles calculations to reveal that LaSb and LaBi are perfectly charge compensated semimetals, explaining their extremely large magnetoresistance and related phenomena through classical electron-hole balance.

Contribution

It demonstrates that perfect charge compensation in LaSb and LaBi accounts for their large magnetoresistance without invoking topological effects.

Findings

LaSb and LaBi are semimetals with balanced electron and hole carriers.

Calculated carrier densities match experimental data, indicating high mobility.

Charge compensation explains XMR, quadratic field dependence, and resistivity plateau.

Abstract

By the first-principles electronic structure calculations, we have systematically studied the electronic structures of recently discovered extremely large magnetoresistance (XMR) materials LaSb and LaBi. We find that both LaSb and LaBi are semimetals with the electron and hole carriers in perfect balance. The calculated carrier densities in the order of $10^{20}$ cm$^{-3}$ are in good agreement with the experimental values, implying long mean free time of carriers and thus high carrier mobilities. With a semiclassical two-band model, the perfect charge compensation and high carrier mobilities naturally explain (i) the XMR observed in LaSb and LaBi; (ii) the non-saturating quadratic dependence of XMR on external magnetic field; and (iii) the resistivity plateau in the turn-on temperature behavior at very low temperatures. The explanation of these features without resorting to the topological effect indicates that they should be the common characteristics of all perfectly electron-hole compensated semimetals.