Spin selective spectroscopy of a quantum dot using tunnel-coupled quantum wires as spin filters

Abstract

A quantum dot (QD) having two tunnel-coupled quantum wires (QWs) was fabricated to probe the QD's spin configuration using the QWs as spin filters. The QWs were adjusted to be either spin-polarized or spin-depolarized under a magnetic field $B$. The spin filtering effect was only observed for spin-polarized QWs, and singlet and triplet states were distinguished for values of the filling factor $2<\ensuremath{\nu}<4$. The spin filtering rate increased due to Zeeman splitting in the QW as the $B$ field was increased, but it decreased dramatically the region of $\ensuremath{\nu}<2$ due to the cotunneling effect.