Anomalous Resistance Ridges Along Filling Factor $\nu = 4i$

TL;DR

This paper reveals unique resistance ridges at filling factors multiples of 4 in SiO$_2$/Si quantum wells, caused by a novel many-body effect involving valley and spin degeneracies, confirmed by magnetic field experiments.

Contribution

It uncovers a new many-body phenomenon manifesting as resistance ridges at $ u=4i$, linked to valley and spin degeneracy interactions in silicon quantum wells.

Findings

Resistance ridges at $ u=4i$ are observed in magnetoresistance.

Ridges disappear under in-plane magnetic field, indicating spin involvement.

Data suggest a new many-body effect involving valley and spin degeneracies.

Abstract

We report anomalous structure in the magnetoresistance of SiO$_2$/Si(100)/SiO$_2$ quantum wells. When Landau levels of opposite valleys are driven through coincidence at the Fermi level, the longitudinal resistance displays elevations at filling factors that are integer multiples of 4 $(\nu=4i)$ accompanied by suppression on either side of $\nu=4i$. This persists when either magnetic field or valley splitting is swept leading to resistance ridges running along $\nu=4i$. The range of field over which they are observed points to the role of spin degeneracy, which is directly confirmed by their disappearance under in-plane magnetic field. The data suggest a new type of many-body effect due to the combined degeneracy of valley and spin.