Coulomb interaction and valley-orbit coupling in Si quantum dots

TL;DR

This study investigates how electron-electron interactions influence valley-orbit coupling in silicon quantum dots with 2 to 4 electrons, finding that such effects are negligible due to interference and cancellation mechanisms, confirmed by experimental spectra.

Contribution

The paper demonstrates that electron-electron interactions do not significantly affect valley-orbit coupling in multivalley Si quantum dots, contrary to prior expectations.

Findings

Electron-electron interactions are negligible in valley-orbit coupling for N=2 to 4.

Valley interference and spinor overlaps suppress interaction effects.

Experimental spectra confirm occupation-independent valley-orbit coupling.

Abstract

The valley-orbit coupling in a few-electron Si quantum dot is expected to be a function of its occupation number N. We study the spectrum of multivalley Si quantum dots for 2 <= N <= 4, showing that, counterintuitively, electron-electron interaction effects on the valley-orbit coupling are negligible. For N=2 they are suppressed by valley interference, for N=3 they vanish due to spinor overlaps, and for N = 4 they cancel between different pairs of electrons. To corroborate our theoretical findings, we examine the experimental energy spectrum of a few-electron metal-oxide-semiconductor quantum dot. The measured spin-valley state filling sequence in a magnetic field reveals that the valley-orbit coupling is definitively unaffected by the occupation number.