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Evidence for spin singlet-triplet transitions of two electrons in a quantum dot observed via single-electron tunneling

1994; Elsevier BV; Volume: 305; Issue: 1-3 Linguagem: Inglês

10.1016/0039-6028(94)90954-7

1879-2758

Bo Su, V. J. Goldman, J. E. Cunningham,

Surface and Thin Film Phenomena

We report magnetotunncling in a double-barrier resonant tunneling nanometer device in the single-electron charging regime, in particular for the case of two electrons in the well. Sharp rising steps appear in current-voltage characteristics, the Nth step appearing at a voltage VN when the Coulomb blockade for tunneling of Nth electron into the well is overcome. The first current step width is ΔV1 = V2 − V1 (the second step width is ΔV2 = V3 − V2), corresponding to the difference of energies required for having two (three) electrons and having one (two) electron(s) in the well. As a function of magnetic field, we observe ΔV1 to exhibit upward cusps, while ΔV2 exhibits downward cusps at the same magnetic field. Such behavior is expected to manifest the spin singlet-triplet transitions of the two-electron state confined in a quantum dot.