Ambipolar transport is a commonly occurring theme in semimetals and semiconductors. Here we present an analytical formulation of the conductivity for a two-band system. Electron and hole carrier densities and their respective conductivities are mapped into a two-dimensional unit-less phase space. Provided that one of the carrier densities is known, the dimensionless phase space can be probed through magnetoresistance measurements. This formulation of the two-band model for conductivity is applied to magnetoresistance experiments on Ca3Ru2O7. While previous such measurements focused on the low-temperature limit, we cover a broad temperature range and find negative magnetoresistance in an intermediate interval below the electronic transition at 48 K. The low-temperature magnetoresistance in Ca3Ru2O7 is consistent with a two-band structure. However, the model fails to describe the full temperature and magnetic field dependence. Negative magnetoresistance found in an intermediate temperature range is, for example, not captured by this model. We thus conclude that the electronic and magnetic structure in this intermediate temperature range render the system beyond the most simple two-band model.
@article{arxiv.2103.15120,
title = {Two-carrier Magnetoresistance: Applications to Ca$_3$Ru$_2$O$_7$},
author = {Lakshmi Das and Yang Xu and Tian Shang and Alexander Steppke and Masafumi Horio and Jaewon Choi and Simon Jöhr and Karin von Arx and Jasmin Mueller and Dominik Biscette and Xiaofu Zhang and Andreas Schilling and Veronica Granata and Rosalba Fittipaldi and Antonio Vecchione and Johan Chang},
journal= {arXiv preprint arXiv:2103.15120},
year = {2021}
}