The role of discrete orbital symmetry in mesoscopic physics is manifested in a system consisting of three identical quantum dots forming an equilateral triangle. Under a perpendicular magnetic field, this system demonstrates a unique combination of Kondo and Aharonov-Bohm features due to an interplay between continuous [spin-rotation SU(2)] and discrete (permutation C3v) symmetries, as well as U(1) gauge invariance. The conductance as a function of magnetic flux displays sharp enhancement or complete suppression depending on contact setups.
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"In the absence of a magnetic field, the currents through the tunneling channels simply add, but in the presence of a perpendicular magnetic field B more complicated superposition pattern arises due to the Aharonov-Bohm effect. Besides, the field B introduces charge chirality into the scheme of classification of electron states of the CQD [34,35]. This type of chirality arises because an electron acquires a U(1) gauge phase / 3 φ = Φ at each tunneling hopping event. "
[Show abstract][Hide abstract]ABSTRACT: We describe in this short review the influence of discrete symmetries in complex quantum dots on the Kondo co-tunneling through these nano-objects. These discrete symmetries stem from the geometrical structure of the tunneling devices (e.g spatial symmetry of multivalley quantum dot in a tunneling contact with leads). They affect the dynamical symmetry of spin multiplets characterizing the ground state and excitations in quantum dots with definite electron number occupation. The influence of external electric and magnetic fields on these symmetries is examined, and analogies with the physics of quantum tunneling through molecular complexes are discussed.
[Show abstract][Hide abstract]ABSTRACT: We investigate the thermoelectric properties of a laterally coupled double-quantum-dot structure. For this structure, a one-dimensional quantum dot (QD) chain between two leads forms a main channel for electron transmission, and each QD in the chain laterally couples to an additional QD. It is found that at low temperature, similar insulating bands emerge around the antiresonant points in the electronic and thermal conductance spectra. And, the edges of the insulating bands become steep rapidly with the increase of QD numbers. What’s interesting is that striking thermoelectric effect exists in the energy region where the insulating bands appear. Furthermore, with the formation of the insulation bands, the magnitude of the Seebeck coefficient becomes stable, whereas the thermoelectric efficiency
is increased. By plotting the Lorentz number spectrum, we observe that in such a structure, the Lorentz number strongly violates the Wiedemann-Franz law in the insulating-band region with its maximum at the point of antiresonance. When weak intradot Coulomb interaction is taken into account, the weakened thermoelectric effect can still be improved with the increase of QD numbers.
No preview · Article · Nov 2012 · Physics of Condensed Matter