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.
Highlights
Semiconductor quantum dots have been known for their excellent electronic properties, and become attractive candidates to realize quantum bits and related spintronic functions [1]
In the Coulomb blockade regime where the sequential tunneling transport is greatly sup-pressed, electron conduction is dominated by cotunneling processes [3,4,5]
The cotunneling transport can be either elastic if the transmitting electron leaves the dot in its ground state, or inelastic if the applied bias exceeds the lowest excitation energy and the dot is left in an excited state
Summary
Semiconductor quantum dots have been known for their excellent electronic properties, and become attractive candidates to realize quantum bits and related spintronic functions [1]. Such spintronic devices are based on a spin control of electronics, or an electrical control of spin in spin-dependent transport through a semiconductor quantum dot [2]. In the Coulomb blockade regime where the sequential tunneling transport is greatly sup-pressed, electron conduction is dominated by cotunneling processes [3,4,5]. Quantum dots are usually modeled as simple semiclassical capacitors to explain Coulomb blockade effect and spinrelated transport phenomenon [6]. Conventional approach like Green’s function or master equation combined with Hubbard model has been quite successful in both the sequential tunneling and cotunneling
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