Browsing by Author "Tarucha, Seigo"

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Level Broadening Effect in Electron Tunneling through Double Quantum Dots with Different g Factors
(2011-04-01)
Huang, Shiu-Ming
;
Tokura, Yasuhiro
;
Akimoto, Hikota
;
Kono, Kimitoshi
;
Lin, Juhn-Jong
The spin bottleneck effect was first observed in vertical double quantum dots with different g factors in high magnetic fields. We further investigate the spin-dependent resonance tunneling through the same quantum dot system in low magnetic fields. There are no resonance tunneling peak lines, even though one of the Zeeman levels is aligned, because the mismatch of the other Zeeman sublevels blocks the resonance tunneling. However, the level broadening effect partially releases the spin-dependent blockade. As a compromise between two effects, one resonance tunneling peak line splits into two peak lines and forms a kink structure. The split of the two current peak lines is half of Zeeman energy difference between two dots. (C) 2011 The Japan Society of Applied Physics
Spin transport from doublet state to triplet state in vertical quantum dots
(2008-04-01)
Huang, Shiu-Ming
;
Akimoto, Hikota
;
Kono, Kimitoshi
;
Lin, Juhn-Jong
;
Tarucha, Seigo
We measured electron transport state spectra of an In(0.05)Ga(0.95)As vertical double quantum dot. Both the ground and excited states of transport spectra from two electrons to three electrons are measured using a large source-drain voltage. In the obtained transition spectrum, the ground state transition from the 1S(2) singlet state to the 1S2P triplet state is observed at 5 T. Zeeman splitting with a g-factor of 0.36 is clearly observed at magnetic fields higher than 5 T. The observation of two Zeeman sublevels instead of three for the triplet state is explained by the spin selection rules for the S(Z) components between the two-electron and three-electron spin states. Transition with the total spin difference between the initial and final states larger than 1/2 is forbidden. Because the transition between doublet states is much longer than electron tunneling, both spin up and spin down can be the initial states from spin transitions. There are four transitions contributing to tunneling processes, but only two energy differences lead to the two Zeeman sublevels in the excitation spectra.