Contrast between spin and valley degrees of freedom

TL;DR

This study investigates how spin and valley degrees of freedom influence the effective mass and related properties of two-dimensional electrons in an AlAs quantum well, revealing contrasting behaviors.

Contribution

It provides the first detailed comparison of how spin and valley occupations differently affect electron effective mass and susceptibilities in 2D systems.

Findings

Effective mass depends on valley occupation but not on spin occupation.

Renormalized g-factor varies with valley occupation.

Conduction-band deformation potential is nearly independent of spin occupation.

Abstract

We measure the renormalized effective mass (m*) of interacting two-dimensional electrons confined to an AlAs quantum well while we control their distribution between two spin and two valley subbands. We observe a marked contrast between the spin and valley degrees of freedom: When electrons occupy two spin subbands, m* strongly depends on the valley occupation, but not vice versa. Combining our m* data with the measured spin and valley susceptibilities, we find that the renormalized effective Lande g-factor strongly depends on valley occupation, but the renormalized conduction-band deformation potential is nearly independent of the spin occupation.