Spin susceptibility and effective mass of two-dimensional electrons in MgxZn1-xO/ZnO heterostructures

TL;DR

This study measures the spin susceptibility and effective mass of two-dimensional electrons in MgxZn1-xO/ZnO heterostructures, revealing their dependence on electron density and electron-electron interactions.

Contribution

It provides the first systematic measurements of spin susceptibility and effective mass in MgxZn1-xO/ZnO heterostructures across various compositions and electron densities.

Findings

Both spin susceptibility and effective mass increase as electron density decreases.

Electron-electron interactions significantly influence the electronic properties.

The results enhance understanding of 2D electron systems in oxide heterostructures.

Abstract

We report measurements of the spin susceptibility and the electron effective mass for two-dimensional electrons confined at the interfaces of MgxZn1-xO/ZnO single heterostructures (x = 0.05, 0.08, and 0.11), grown by molecular-beam epitaxy on (0001) ZnO substrates. By tuning the built-in polarization through control of the barrier composition, the electron density was systematically varied in the range of 5.6 x 10^11 to 1.6 x 10^12 cm^-2, corresponding to a range of 3.1 < rs < 5.2, where rs is the average electron spacing measured in units of the effective Bohr radius. We used the coincidence technique, where crossings of the spin-split Landau levels occur at critical tilt angles of magnetic field, to evaluate the spin susceptibility. In addition, we determined the effective mass from the temperature dependence of the Shubnikov-de Haas oscillations measured at the coincidence conditions. The susceptibility and the effective mass both gradually increase with decreasing electron density, reflecting the role of electron-electron interaction.