We analyzed the electronic transport through a double quantum dot in the spin blockade regime. Experiments of current rectification by Pauli exclusion principle in double quantum dots were discussed. The electron and nuclei spin dynamics and their interplay due to the Hyperfine interaction were self-consistently analyzed within the framework of rate equations. Our results show that the current leakage experimentally observed in the spin-blockade region, is due to spin-flip processes induced by Hyperfine interaction through Overhauser effect. We show as well how a magnetic field applied parallel to the current allows excited states to participate in the electronic current and removes spin blockade. Our model includes also a self-consistent description of inelastic transitions where the energy is exchanged through interactions with acoustic phonons in the environment. It accounts for spontaneous emission of phonons which results in additional features in the current characteristics. We develop a microscopical model to treat the Hyperfine interaction in each dot. Using this model we study the dynamical nuclear polarization as a function of the applied voltage.PACS numbers:
We analyze theoretically the dependence of the longitudinal magnetoresistivity response of microwave irradiated two-dimensional electron systems on the microwave polarization. Both linear and circular polarizations are considered. Recent experiments show that resistivity oscillations and zero resistance states are unaffected by changing the polarization of the microwave field. We propose a plausible explanation for the experimentally observed magnetoresistivity polarization immunity.Recently, magnetotransport experiments on twodimensional electron systems ͑2DESs͒ irradiated with microwaves have shown two very interesting features: microwave induced resistivity oscillations 1,2 ͑MIROs͒ and zero resistance states ͑ZRSs͒. 3,4 This has motivated intense activity, both experimental and theoretical. New and remarkable experimental contributions are being published on a continual basis. Among them, one can note the activated temperature dependence in the magnetoresistivity ͑ xx ͒ response, [3][4][5] quenching of xx at high microwave ͑MW͒ intensities, 2,6 absolute negative conductivity, 2,5-7 suppression of MIRO and ZRS by in-plane magnetic field, 8,9 and the behavior of xx under bichromatic MW radiation coming from two monochromatic sources with different frequencies. 10 Possibly the observation that MIRO and ZRS are notably immune to the polarization of MW radiation in Ref. 11 is one of the most surprising results. In this experiment, the influence of the MW polarization on xx in a 2DES was analyzed. Different MW polarizations were used, circular in both senses ͑left and right͒ and also linear in x ͑current direction͒ and y directions. The unexpected result of almost complete immunity of xx with the polarization was obtained. All these experimental results provide real challenges for the theoretical models presented to date. [12][13][14][15][16][17][18][19][20][21][22] Some theoretical contributions have been presented that can explain some of the experimental outcomes. We note proposals for explaining the behavior of the MW driven xx with temperature and with high MW intensities, 23,24 the observed absolute negative conductivity, 25,26 and the xx response to bichromatic MW radiation. 27,28 Regarding MWpolarization immunity, while some theoretical models predict strikingly different dependences on the radiation polarization, 14,18,20 in others only linear radiation was considered. 16,17,19 In this Brief Report, we propose a theoretical explanation for the experimental evidence which shows that xx does not depend on the MW polarization. Our theoretical results are based on the driven Larmor orbits model. 19 In our recently presented work, 19 we showed that in a 2DES subjected to a moderate perpendicular magnetic field and MW radiation, the Larmor orbit centers oscillate back and forth in the x direction with the same frequency as the MW field. A major and nontrivial extension of this model 19 is presented here, which allows different polarizations for the MW field to be considered, namely, elliptical, circular, or linea...
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