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

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<ν<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 ν<2 due to the cotunneling effect.