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Electron cotunneling through doubly occupied quantum dots: effect of spin configuration.

Lan J, Sheng W - Nanoscale Res Lett (2011)

Bottom Line: A microscopic theory is presented for electron cotunneling through doubly occupied quantum dots in the Coulomb blockade regime.Beyond the semiclassic framework of phenomenological models, a fully quantum mechanical solution for cotunneling of electrons through a one-dimensional quantum dot is obtained using a quantum transmitting boundary method without any fitting parameters.Furthermore, it is found that the cotunneling conductance reveals more sensitive dependence on the barrier width than the height.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Furan University, Shanghai 200433, PR China. shengw@fudan.edu.cn.

ABSTRACT
A microscopic theory is presented for electron cotunneling through doubly occupied quantum dots in the Coulomb blockade regime. Beyond the semiclassic framework of phenomenological models, a fully quantum mechanical solution for cotunneling of electrons through a one-dimensional quantum dot is obtained using a quantum transmitting boundary method without any fitting parameters. It is revealed that the cotunneling conductance exhibits strong dependence on the spin configuration of the electrons confined inside the dot. Especially for the triplet configuration, the conductance shows an obvious deviation from the well-known quadratic dependence on the applied bias voltage. Furthermore, it is found that the cotunneling conductance reveals more sensitive dependence on the barrier width than the height.

No MeSH data available.


Related in: MedlinePlus

Cotunneling conductance calculated as a function of the applied bias voltage for the dot occupied by a singlet (thin lines) and triplet (thick lines).
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Figure 2: Cotunneling conductance calculated as a function of the applied bias voltage for the dot occupied by a singlet (thin lines) and triplet (thick lines).

Mentions: In the Coulomb blockade regime where the sequential tunneling transport is greatly suppressed, e.g., when V < 10 mV in Figure 1 electron conduction is dominated by cotunneling processes [4,5]. Figure 2 plots the conductance of electron cotunneling through a dot occupied by a singlet and triplet. Since cotunneling current is generally several orders of magnitude smaller than the sequential tunneling, we have to set the precision for the iterative solver to be 10-6 to obtain reliable result. For the case of a singlet in the dot, it is seen that the cotunneling conductance closely follows the well-known quadratic dependence [13] on the applied bias voltage. The cotunneling conductance in the case of a triplet is found not only generally larger than the singlet but also deviates obviously from the quadratic dependence. Actually, the conductance is seen to be almost linear with the bias voltage with a very small quadratic term. For comparison, the conductance of electron cotunneling through a singly occupied quantum dot exhibits very little dependence on the spin configuration of the incident and confined electrons [14]. Furthermore, it exhibits much less deviation from the quadratic dependence than the cotunneling conductance for the triplet configuration.


Electron cotunneling through doubly occupied quantum dots: effect of spin configuration.

Lan J, Sheng W - Nanoscale Res Lett (2011)

Cotunneling conductance calculated as a function of the applied bias voltage for the dot occupied by a singlet (thin lines) and triplet (thick lines).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211313&req=5

Figure 2: Cotunneling conductance calculated as a function of the applied bias voltage for the dot occupied by a singlet (thin lines) and triplet (thick lines).
Mentions: In the Coulomb blockade regime where the sequential tunneling transport is greatly suppressed, e.g., when V < 10 mV in Figure 1 electron conduction is dominated by cotunneling processes [4,5]. Figure 2 plots the conductance of electron cotunneling through a dot occupied by a singlet and triplet. Since cotunneling current is generally several orders of magnitude smaller than the sequential tunneling, we have to set the precision for the iterative solver to be 10-6 to obtain reliable result. For the case of a singlet in the dot, it is seen that the cotunneling conductance closely follows the well-known quadratic dependence [13] on the applied bias voltage. The cotunneling conductance in the case of a triplet is found not only generally larger than the singlet but also deviates obviously from the quadratic dependence. Actually, the conductance is seen to be almost linear with the bias voltage with a very small quadratic term. For comparison, the conductance of electron cotunneling through a singly occupied quantum dot exhibits very little dependence on the spin configuration of the incident and confined electrons [14]. Furthermore, it exhibits much less deviation from the quadratic dependence than the cotunneling conductance for the triplet configuration.

Bottom Line: A microscopic theory is presented for electron cotunneling through doubly occupied quantum dots in the Coulomb blockade regime.Beyond the semiclassic framework of phenomenological models, a fully quantum mechanical solution for cotunneling of electrons through a one-dimensional quantum dot is obtained using a quantum transmitting boundary method without any fitting parameters.Furthermore, it is found that the cotunneling conductance reveals more sensitive dependence on the barrier width than the height.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Furan University, Shanghai 200433, PR China. shengw@fudan.edu.cn.

ABSTRACT
A microscopic theory is presented for electron cotunneling through doubly occupied quantum dots in the Coulomb blockade regime. Beyond the semiclassic framework of phenomenological models, a fully quantum mechanical solution for cotunneling of electrons through a one-dimensional quantum dot is obtained using a quantum transmitting boundary method without any fitting parameters. It is revealed that the cotunneling conductance exhibits strong dependence on the spin configuration of the electrons confined inside the dot. Especially for the triplet configuration, the conductance shows an obvious deviation from the well-known quadratic dependence on the applied bias voltage. Furthermore, it is found that the cotunneling conductance reveals more sensitive dependence on the barrier width than the height.

No MeSH data available.


Related in: MedlinePlus