Magnetoresistance in Dilute $p$-Si/SiGe in Parallel and Tilted Magnetic Fields

TL;DR

This study investigates magnetoresistance in p-Si/SiGe samples under various magnetic field orientations and temperatures, revealing the influence of in-plane magnetic fields on orbital motion and spin level overlaps affecting quantum Hall anomalies.

Contribution

It provides new insights into the effects of tilted magnetic fields on magnetoresistance and spin level interactions in dilute p-Si/SiGe systems.

Findings

Large in-plane magnetoresistance due to orbital effects.

Anomaly at filling factor 3/2 is negligible in conductivity.

Level overlap explains the anomaly at filling factor 2.

Abstract

We report the results of an experimental study of the magnetoresistance $\rho_{xx}$ and $\rho_{xy}$ in two samples of $p$-Si/SiGe with low carrier concentrations $p$=8.2$\times10^{10}$ cm$^{-2}$ and $p$=2$\times10^{11}$ cm$^{-2}$. The research was performed in the temperature range of 0.3-2 K and in the magnetic fields of up to 18 T, parallel or tilted with respect to the two-dimensional (2D) channel plane. The large in-plane magnetoresistance can be explained by the influence of the \textit{in-plane} magnetic field on the orbital motion of the charge carriers in the quasi-2D system. The measurements of $\rho_{xx}$ and $\rho_{xy}$ in the tilted magnetic field showed that the anomaly in $\rho_{xx}$, observed at filling factor $\nu$=3/2 is practically nonexistent in the conductivity $\sigma_{xx}$. The anomaly in $\sigma_{xx}$ at $\nu$=2 might be explained by overlapping of the levels with different spins 0$\uparrow$ and 1$\downarrow$ when the tilt angle of the applied magnetic field is changed. The dependence of g-factor $g^*(\Theta)/g^*(0^0)$ on the tilt angle $\Theta$ was determined.