Magnetoresistance in Two-Component Systems

Two-component systems with equal concentrations of electrons and holes exhibit nonsaturating, linear magnetoresistance in classically strong magnetic fields. The effect is predicted to occur in finite-size samples at charge neutrality due to recombination. The phenomenon originates in the excess quasiparticle density developing near the edges of the sample due to the compensated Hall effect. The size of the boundary region is of the order of the electron-hole recombination length that is inversely proportional to the magnetic field. In narrow samples and at strong enough magnetic fields, the boundary region dominates over the bulk leading to linear magnetoresistance. Our results are relevant for two-and three-dimensional semimetals and narrow band semiconductors including most of the topological insulators.

Figure 1

Electron (green) and hole (red) trajectories in an electron-hole symmetric setup at charge neutrality. The bulk of the sample exhibits large geometric MR as a consequence of the compensated Hall effect: electron and hole trajectories are tilted but the Hall voltage is absent. Lateral quasiparticle flow $\mathit{P}$ results in excess quasiparticle density near the sample edges, where recombination processes due to electron-phonon interaction lead to linear MR.

Figure 2

Sheet resistance $R_{\square }$ at charge neutrality versus magnetic field [Eq. (13)] for three different values of the ratio $W/{\ell }_0$. The resistance is rescaled for better presentation.

Figure 3

Sheet resistance $R_{\square }$ (top) versus magnetic field as given by Eq. (17) for $W/{\ell }_0=10$ and different values of the parameter $\xi =n_0/{\rho }_0$. The bottom panels illustrate the spatial profiles of the quasiparticle current [Eq. (11)] and density [obtained from Eq. (9c)] at charge neutrality for $W/{\ell }_R=10$ that are measured in the units of $P_B$ and ${\rho }_B=2P_B{\tau }_R/{\ell }_R$.