Valley susceptibility of an interacting two-dimensional electron system

TL;DR

This study measures how the valley population in an AlAs 2D electron system responds to strain, revealing a significant increase in valley susceptibility at lower densities due to strong electron-electron interactions, similar to spin susceptibility.

Contribution

It provides the first direct measurement of valley susceptibility in an interacting 2D electron system, highlighting the analogy between spin and valley degrees of freedom.

Findings

Valley susceptibility increases as density decreases.

Strong electron-electron interactions enhance valley susceptibility.

Resembles the behavior of spin susceptibility in similar systems.

Abstract

We report direct measurements of the valley susceptibility, the change of valley population in response to applied symmetry-breaking strain, in an AlAs two-dimensional electron system. As the two-dimensional density is reduced, the valley susceptibility dramatically increases relative to its band value, reflecting the system's strong electron-electron interaction. The increase has a remarkable resemblance to the enhancement of the spin susceptibility and establishes the analogy between the spin and valley degrees of freedom.