3 resultados para Fórmula de Landauer

em University of Queensland eSpace - Australia


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We show that an Anderson Hamiltonian describing a quantum dot connected to multiple leads is integrable. A general expression for the nonlinear conductance is obtained by combining the Bethe ansatz exact solution with Landauer-Buttiker theory. In the Kondo regime, a closed form expression is given for the matrix conductance at zero temperature and when all the leads are close to the symmetric point. A bias-induced splitting of the Kondo resonance is possible for three or more leads. Specifically, for N leads, with each at a different chemical potential, there can be N-1 Kondo peaks in the conductance.

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We theoretically study thermal transport in an electronic interferometer comprising a parallel circuit of two quantum dots, each of which has a tunable single electronic state which are connected to two leads at different temperature. As a result of quantum interference, the heat current through one of the dots is in the opposite direction to the temperature gradient. An excess heat current flows through the other dot. Although locally, heat flows from cold to hot, globally the second law of thermodynamics is not violated because the entropy current associated with heat transfer through the whole device is still positive. The temperature gradient also induces a circulating electrical current, which makes the interferometer magnetically polarized.

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We introduce a spin-charge conductance matrix as a unifying concept underlying charge and spin transport within the framework of the Landauer-Buttiker conductance formula. It turns out that the spin-charge conductance matrix provides a natural and gauge covariant description for electron transport through nanoscale electronic devices. We demonstrate that the charge and spin conductances are gauge invariant observables which characterize transport phenomena arising from spin-dependent scattering. Tunnelling through a single magnetic atom is discussed to illustrate our theory.